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In a battery-powered electric vehicle, regenerative braking (also called regen) is the conversion of the vehicle’s kinetic energy into chemical energy stored in the battery, where it can be used later to drive the vehicle. It is braking because it also serves to slow the vehicle. It is regenerative because the energy is recaptured in the battery where it can be used again.

The kinetic energy stored in a moving vehicle is related to the mass and speed of the vehicle by the equation E = ½mv². All else being equal, if your car is twice as heavy it has twice the kinetic energy and if it is moving twice as fast it has four times the kinetic energy. Any time your car slows down the kinetic energy stored in the vehicle has to go somewhere. Let’s take a look at where this energy goes. There is always some kinetic energy consumed by the rolling resistance, mechanical friction, and aerodynamics of your car. These bits of energy go into heating the road, the surrounding air, and various spinning parts in your car. But the vast majority of the kinetic energy is converted into heat by your brake pads when you stomp on the brakes. In the Tesla Roadster, regenerative braking recovers some energy that would otherwise have been wasted in the brakes.

How much energy does it recover?

Unfortunately, the adage “your mileage may vary” applies to regen as well. The amount of energy you can recover depends on how and where you drive. From the powertrain point of view it looks pretty good. The energy conversion efficiencies from chemical to electrical (battery), DC current to AC current (inverter), electrical to mechanical (motor), and torque to force (transmission and wheels) are all quite high and work just as efficiently returning energy into the battery. The bigger problem is aerodynamic losses and higher speeds and rolling friction of the tires. These both act to slow the car, but the energy dissipated cannot be recovered. We must also remember that, even though the battery-to-wheel conversion efficiency is pretty good (up to 80% or so), the energy makes a full circle back into the battery and it gets converted twice for a net efficiency of at most 80% * 80% = 64%.

How does it work?

Due to the simplicity of the AC induction motor’s single moving part, the Tesla Roadster does not experience the engine compression braking of a traditional internal combustion engine (ICE). Instead, the advanced algorithms in the motor controller give it complete control of the motor torque for both driving and regenerative braking. A torque command is derived from the position of the throttle pedal. The motor controller converts this torque command into the appropriate 3-phase voltage and current waveforms to produce the commanded torque in the motor in the most efficient way. The torque command can be positive or negative. When the torque serves to slow the vehicle then energy is returned to the battery and presto - we have regenerative braking!

I should also note that the motor and controller can deliver the torque command at any operating speed, including 0 mph. This means that we can regen the car to a complete stop. But as a practical matter, the kinetic energy of a slowly moving car is low enough that very little energy is put back into the battery as the car comes to a stop. In fact, the last little bit of slowing the vehicle down generates such a small amount of energy that it does not even cover the fixed losses in the inverter and motor.

When does it work?

There are a number of goals and restrictions when using regenerative braking. Tesla Motors is still putting the final touches on the regen torque profile to achieve the goals within the constraints.

Safety: Negative torque applied to the rear wheels can cause a car to become unstable. Since regen braking is a source of negative torque, the Tesla Roadster uses the traction control system to limit regen if the rear wheels start to slip. I was part of the team that developed and verified this safety feature on a frozen lake in Arvidsjaur, Sweden.

Performance: Regenerative braking can enhance the driving experience in ways not available with a traditional internal combustion engine (ICE). Driving with regen is fun! Having that instant positive and negative torque command right at your toes really make you feel in control.

Limitations: Regenerative braking is necessarily limited when the batteries are fully charged. Because the additional charge from regenerative braking would cause the voltage of a full battery to rise above a safe level, our motor controller will limit regen torque in this case.

The future for regenerative braking

There are a number of subjective decisions we have to make concerning the regen profile. Some people like regen to work all the way to 0 mph, bringing the car to a complete stop. Others like to coast that last 2 to 3 mph. Almost everyone likes the car to regen when you take your foot off of the throttle pedal, but there are some who would prefer the car to coast when you do this. They would prefer the regen to be tied to the application of the brake pedal. Almost everyone likes the more aggressive regen available to the driver, but a few people are more comfortable with a traditional ICE-like compression braking and coast-down profile. Ultimately, the Tesla Roadster is a sports car and the regen profile will be fine tuned for sports car driving.

One day everyone will drive electric cars and regen will be a big part of what will make them fun to drive, efficient, and safe. The recent research and development to integrate the powertrain and brake systems to provide better traction and stability control can only be made easier by the use of electric drive systems. One thing I learned from the traction control work I did on the frozen lake is that traction control is a much simpler problem to solve when you have precise and instant control of torque through the AC induction motor controller. Further integration of antilock braking systems with the motor controller would allow the motor to take over more of the vehicle braking. It’s very exciting to be working at the forefront of these possibilities.

Wow, that's cool stuff, Greg. I hadn't thought much about the benefits of electric drive in traction control and ABS, but it seems obvious now. I'm interested to know whether there will be provisions for different regen profiles available to the driver to handle the subjective concerns you mention. All in all, I agree with your choices, but it still seems like it would be good (and easy) to let the driver decide for himself what he likes. Similarly, is there going to be a way to set the roadster to just charge to (say) 90%, so that the regen profile won't be different when you start driving? I can imagine I'd be annoyed by a car that felt completely different in the throttle for the first 20 miles.

Joseph

4:07pm | Jun 29, 2007

Regenrative braking rules!

CM

4:09pm | Jun 29, 2007

It should be possible to continue regenerative braking when the batteries are full by diverting the excess power to a resistance bank cooled by a fan, like a giant blow dryer. This could make an ultra-reliable fade-proof braking system, suitable for long downhill runs. Other cars rely on downshifting and engine braking to avoid overheating the brake pads and suffering brake failure. Tesla can do it better.

Doug @ Stanford

4:36pm | Jun 29, 2007

"There are a number of subjective decisions we have to make concerning the regen profile. Some people like ..."
So why not make it user selectable? The traction control should still take over if too much regen causes a problem.

The Roadster will initiate regenerative braking when the accelerator is released, and will through a "black box" calculate the amount of regenerative braking that will take effect.

Or will the driver be in a position to adapt the regenerative braking to their personal preference. An electric car can coast for quite a distance compared to an car with an ICE.

Intuitively braking initiates by appliying pressure on the brake pedal, not releasing the accelerator, it must be quite the experience driving a car that starts braking as the accelerator is released.

Would the regenerative braking diminish as the brakes are applied?

Marcus

5:16pm | Jun 29, 2007

Thanks for a very informative and interesting post. Looking forward to that one day when everyone will drive electric......

Ryan Lamansky

5:22pm | Jun 29, 2007

Does the Tesla Roadster apply a stronger regen profile when the brake pedal is touched, but before the friction brakes connect?

This seems ideal to me when you want more braking force than the foot-off-the-go-pedal profile provides, but still want to conserve energy...

Sia

5:33pm | Jun 29, 2007

Smart, no "buts" about it either, However;

-Have you guys thought about "Adaptive Control"(AC)?

Basically, " an A.I. in the form of simple algorithm", where ;

1-when activated, A.I. records certain Measurable Parameters(MPs) over a preiod of time, say 2 weeks( worth of driven hours(dh) for the sake of argument.
Let's face it, Telsa drivers, are most likely going to "produce" a limited range of MPs, since they are not likely to put their Telsa into conditions such as, Rough off-roading, steep angle climbing, third world road conditions, hazzardous wasteland etc:-)

2-Simple MPs will include parameters such as;
2.1-Average Horizon Angle over the period of 2 weeks.
2.2-Average speed at time intervals.
2.3-Average speed in different times and days of the week.
2.4-Average "Door Open Door Closed"
2.5-Average "Passenger Mass".
2.6-Average Cargo Mass.
2.7-Average temperature and Humidity.
2.8-Average Pripheral Device Use.
2.9-Average "accel/decel" length and intervals.
2.10-Average "Roll, Pitch and Yaw".
2.11-Average number of "Tractin Control Activations".
2.12-Average Drag ETC ETC ETC....

3-When A.I has calculated all averages, through a symple algorythm, such as , say, Standar Deviation Methodology, the driver will then be given the choice of either;

3.3-Activation of A.I to control "Regen"
3.4-Continue with a manual chopice of Regen( i.e. Braking), at wich time A.I. will continue to capture data for future use!

If I were to invest almost 100K in my dream Telsa, I would not mind spending another 10K in A.I. Would you?

Whoa Greg! Double Whammy - your face is on the Touch and Hear blogs at the same time.
Nice going. That is a first.

The most interesting part (to me) of reading this blog entry was to see the terminology phrases that you use when describing what you do. You could have described it different ways, and from different perspectives, but I thought these particular phrases told a bit of a story of how you look at things:

## "A torque command is derived from the position of the throttle pedal."
## "...the regen torque profile to achieve the goals within the constraints"

Some other companies note that they have some sort of shunt resistor to turn excess regen energy into heat when the batteries are full. It sounds like you decided not to go that route and simply cut back on regen when you dont need it... (?)
Wouldn't it be a better overall driving experience if the regen was consistent and you just threw away any extra energy recaptured when you didn't need it?
I would find it disconcerting if I usually got a little bit of slow down from lifting the throttle, but then halfway down a hill I started "rolling" more than usual.

# Greg Wrote:
## Some people like regen to ...
## Others like to coast ...
## Almost everyone likes...
## but there are some who would prefer ...
## but a few people...

Here is another suggestion to consider adjustable regen. Perhaps a knob with 3 or 4 profiles to pick between?
I like the idea of sliders to adjust the parameters, but I know infinite choices require infinite testing...

JoeG

11:01pm | Jun 29, 2007

Great stuff.

I presume that these features of regen braking will be available in the Whitestar too. What will be the primary difference in the regen to give the Whitestar a sport sedan feel rather than a roadster feel?

Will there be any modes programmed in so that a user can switch to brake-only regen mode and another driver can switch to active-regen? Similar to the seat and mirror positions of most luxury sedans.

Malcolm Wilson

2:05am | Jun 30, 2007

Thanks Greg

Since Tesla encourage owners to recharge Li-ions to 100% only when needed in order to prolong calender life (see "A Bit About Batteries") temporary loss of regen due to a fully charged battery should be a fairly rare event. Of course, from a design point of view, 100% charge does not actually have to be 100% but could be 99% instead (rather like Spinal Tap's Amps going up to 11). So the battery pack always has some regen headroom.

Since the car only has two gears, presumably regen is programmed to vary with speed. To what extent is regen efficiency compromised by the need for a familiar ICE engine-braking feel?

Given the subjective nature of fine-tuning the regen profile, will there be a facility for Tesla to field-trial different regen profiles by offering these as software downloads to interested owners? Matching acceleration profiles could be offered as well.

Bernhard

5:56am | Jun 30, 2007

Are there any plans to make the regen torque profile user customizable (e.g. coasting when releasing throttle).
Or even better change-able on the run? In the city instant regen would be favorable, also on downhill tracks a constant brake torque would be welcome. An integration of regen with the cruise control system would be best.

Finally a new post, I'm sure you guys are busy but we miss the updates.

So which area of the curve will the regen braking end up, more like and ICE or more coasting like a golf cart? I can see where it would be great fun on an autocross track to have lots of regen when you lift the throttle.

When will we have some information on the release date of the first cars to customers?
Philip

Rich

7:12am | Jun 30, 2007

Another fascinating blog. Regen is so cool. Has anyone at Tesla looked into computer controlled regen shock absorbers. U.S. patent# 6952060. Don’t know how feasible but from the patents it looks like another good source of energy with a controlled ride benefit. Better mileage from bumpy roads!

vfx

9:17am | Jun 30, 2007

Another vote for user adjustable regen (like the Ebox). The 4 to 7 setting knob/switch idea would be ok if it made the feature more technically feasible, otherwise a slider would be prefered.

James Anderson Merritt

10:19am | Jun 30, 2007

Over in audio engineering, they now have software systems (sometimes built directly into microphones or speakers), which allow sound transducers to mimic any of a number of legendary speakers and microphones of the past, at the flip of a switch or the click of a mouse. Perhaps the roadster could be adjusted to perform, in terms of handling and perceived engine response/braking, like any of a select set of legendary sports cars, in addition to having several uniquely optimized performance profiles of its own. Since you probably couldn't use the original marque-names because of trademark restrictions, you might name each mimic-profile for the town or region where the original car was designed or produced, or with some other suggestive name. A profile mimicking BMW might be named "Munich," for example. For Ferrari, "Modena." For Mazda RX-7, "Honshu" (the island that is home to Mazda, avoiding bad associations with their home town of Hiroshima). For Mustang, "Pony," and so forth.

Any "driver memory" feature in the car would automatically switch the performance profile to whichever one the driver in question preferred (or was last using). So the Roadster (or later, the Whitestar) could actually and automatically be very much a different car for each of its different drivers! The key would seems to be to make available only profiles that achieved some important goal (for handling in various conditions or with respect to various driving styles, for energy efficiency, safety, etc.), and to make the selection of a profile as straightforward and effortless as possible. Such a thing would be very cool, indeed, but what happens, and how would the car behave, when "intelligent systems" fail?

Joseph

11:17am | Jun 30, 2007

"It should be possible to continue regenerative braking when the batteries are full by diverting the excess power to a resistance bank cooled by a fan"

I know very, very little about electronics but when you're going 30mph and slam the brakes, a lot of energy is going to go into that resistor, and very, very quickly. A car needs to have the ability to slam on the brakes without a problem, and I suspect that perhaps a resistor wouldn't be reliable enough. (But then again, I know next to nothing about electronics) Another problem with a resistor might be all the heat it generates; perhaps a safety or cooling issue prevented them from using the resistor?

#TEG2- wrote that
# Greg Wrote:
## Some people like regen to …
## Others like to coast …
## Almost everyone likes…
## but there are some who would prefer …
## but a few people…

Why on earth didn't Tesla Motors allow people to set regen for themseleves?!?
I know that regen is complicated (coast, or no coasting? if you do coast, how much coasting? Should the coasting feel like engine braking in an ICE? ect. ect.) but people should still be able to control functions like the strength of the regen whether regen will function to slow the car down for last 2-3mph.
Wouldn't a good solution to all the different people's likings be different settings for regen? You can have a regen driving mode for ICE mode and EV mode.
ICE mode can have regen follow a gas car's braking feel and settings as closely as possible. EV mode can allow a car to coast (without regen coming on to copy the "engine braking" on an ICE).

Having regen setttings available for the person to adjust themselves along with different regen modes is probably a little complicated. However, it will open your product to a bigger crowd. People who are still a little attatched to ICE may like the benefits of having their driving experience closely follow their driving experience in a gas car. Hard-Core EV lovers may like the ability to cost and other distinctively "EV" features.

Robert Horning

2:27pm | Jun 30, 2007

Finally a good answer about what happens when you go down a steep hill with a fully charged battery: The regenerative brakes simply won't be as effective. This could be a bad thing in terms of going down a very steep and long incline downhill. Usually when using and ICE, I use as much engine breaking as possible, depending upon the friction of the internal parts of the ICE to be able to slow my vehicle down enough that I don't have to apply the brakes so much.

Obviously you have to apply brakes even with an ICE, but reducing the brake usage when going down a long hill in mountainous areas can be a very critical thing to worry about. Brake failure (generally for vehicles like semi-trucks) is unfortunately a fairly common occurrence to the point that seeing "runaway truck ramps" and other highway safety features installed to help prevent a brake failure. Dropping 2000 feet of elevation (not even the largest drop you can get) will also release a huge amount of potential energy, and it is this energy that is being applied as kinetic energy to your vehicle which in turn is being transformed into heat, usually on the break pads. This is where brake failures occur on steep hills, as sometimes the break pads literally overheat from trying to remove so much kinetic energy in your vehicle.

Anyway, this is a good post here, and something which has been the subject of several threads of discussion. Thanks Greg!

Alex B

5:47pm | Jun 30, 2007

Hey Greg,

Very interesting and informative post. I understand that the Tesla Roadster would use a combination of friction and regenerative breaking methods. Just out of curiosity - compared to traditional friction breaks (break pads onto break disc) how effective would regenerative breaking be in terms of stopping distances and smootness if hypothetically, the Tesla Roadster would solely rely on this type of breaking system?

Thanks,

Alex

Mark Tomlinson

7:31pm | Jun 30, 2007

One thing I noticed you didn't mention is the idea some companies are toying with to throw the regen power into super caps. The way I understand it, these would provide a reservoir for energy that the battery can't take on. They would be tapped for acceleration and excess could be bled into the batteries as capacity becomes available. Presumably, this would keep the braking profile consistent over the entire trip and prevent wasted energy.

Since we are dealing with a vehicle where the only source of energy is the battery, there isn't much worry about over-charging. Excessive regeneration could be a problem in a hybrid, but isn't likely in an all-electric. You draw energy to climb a hill and get back some of it going down the other side. You accelerate and get back some of the energy braking. Adding a resistive bank would increase vehicle weight and be used very rarely. Net loss. The only case I can think of is if you start with a 100% charge and immediately drive down a long hill.

My driveway is 3200 feet long and entails a 300 foot drop. I'll have to restrict my Whitestar to a 95% charge.

AC Propulsion put a slider in der Ebox that you can put from 0 to 100 % Regenerative bracking. I think this is the best solution for every driving situation.

Release the car in Europa 2010. The gas prices her are 7.5 dollar/gallon
I wish you all big success.

David Kosowsky

7:39am | Jul 1, 2007

Glad to see a post about regen, but would have liked a little more detail. Do you expect regen to be treated the same in the White star? what is the force range that you are testing for max lift-off regen? Others comments have expressed concern about functional inconsistencies by turning off regen when batteries ane full. I agree this shouldn't be done automatically but as much for liability issues as anything else. Ideally region should be:
1.) Lift-off activated up to a set, consistent level.
2.) Resistance shunted for excess power that battery cannot handle.
3.) Additional regen via brake pedal.
4.) Regen lift-off deactivate/ activate button, similar to ABS control in many cars.

Obviously this is much easier said than done, but it would allow for consistent responsiveness. It would also allow for all of the differing wishes of the drivers as described in Greg's entry and in other's comments. Tesla wouldn't have to make the subjective decisions. Another benefit, would be the additional energy that could be recaptured Via the brake pedal regen.

This all seems very simplistic, so I assume it was decided against. If so, can Tesla enumerate any of the factors that led to these decisions?

chris

11:42am | Jul 1, 2007

have you thought of using a live storage device like beacon power to store the regen power then apply it when the batterys are depleted just a thought
the koala http://www.beaconpower.com/

murray

1:44pm | Jul 1, 2007

Like most commenters before me, I'm curious about the possibility of a user-adjustable regen torque profile. The only thing I can add is that it seem to me that a nice way to implement this would be to tie it to the shifter. I see from the image gallery that the shifter has only two positions, but if it could be made fully variable between 1 and 2, its position could dictate the torque profile, such that it can be used to apply the equivalent of engine-braking in an ICE vehicle with manual transmission.

Is this company public yet? How could I become an investor? Looking for that info. Car and company seem like a winner. THANKS

Dr Dave

6:08pm | Jul 1, 2007

Great article! The electric motor goes both ways like a thermos - keeps my tea cold in summer and my coffe hot in winter. How do it know?
All seriousness aside, I've increased my gas mileage driving in the CO mountains by about 15% by shifting to neutral and coasting down every hill. I'd hope to have the same privilege with my first electric, hopefully increasing my range, i.e. to either select the regen profile or have none unless I touch the brake or shift into regen like the Lexus Rx400H does. Thanks for a layman's description even I can follow!

Joseph

8:22pm | Jul 1, 2007

Everyone seems concerned that when batteries are full and only brakes can be used that the difference b/w the two brakes will be appearent and cause a safety issue due to the different feels of the two different brakes.

I wouldn't be concerned, I'm sure Tesla Motors is working to keep the brakes feel as close as possible to the regen braking and vice versa. It's all about intergrating the two different stopping forces together. Toyota and Honda are doing a great job on that with their hybrids, and I'm sure the roadster will be no different.

A comment on marketing the WhiteStar. You should give maybe 100-1000 pre-production WhiteStars to normal customers to test their reliability and to test the market. GM has done this for the EV1 and is soon going to do it for their FCV.
It'll create lots of buzz for Tesla Motors!

# Robert Horning wrote on June 30th, 2007 at 3:27 pm
## Finally a good answer about what happens when you go down a steep hill with a fully charged battery:
## The regenerative brakes simply won’t be as effective. This could be a bad thing in terms of going down a very steep and long incline downhill.

This is probably particularly relevant to someone like Martin who lives at the top of a hill, and starts his daily journey (with fully charged Roadster) going downhill for quite a while. Sure the conventional brakes can do the slowing job, but with wear on them, and wasted energy. Perhaps Martin will have a way to charge his roadster to only 80% (or whatever is ideal) so that the coast down the hill just regens enough to get it to 100% as he hits the flatlands.

=============================================================

I heard that some Diesel-Electric hybrid trains don't have a way to store energy (e.g.: no batteries), but the eMotors do regen when slowing for the next station. Rather than charge batteries, they power cooling fans that cool the engine. You could do something similar with a BEV. When you invoke regen and the batteries are 100% full you could send the power to some fans that blow more air on the eMotor or even the brake calipers.

Malcolm Wilson

11:28pm | Jul 1, 2007

#Dr Dave wrote
# I’ve increased my gas mileage driving in the CO mountains
# by about 15% by shifting to neutral and coasting down every hill.

Interesting. As well as pedal control, link the strength of regen to some sort of on-board artificial horizon so that the car "knows" when it's going down a steep incline.

kert

12:35am | Jul 2, 2007

About user adjustability: this makes safety certification harder. You have to make sure that you dont get into unknown controllability zones with EACH of these settings. Its not a track car, where you tune your suspension a bit this way or that, and let the driver find out how it affects handling. You have to have controlled handling at all possible speeds at all possible settings period. Otherwise, recalls and lawsuits will follow.
I think Tesla will leave these "user adjustments" to aftermarket.

About limiting regen when batteries are full: a simple resistor wouldnt work, you have to have a honest big heating coil. This would have to be able to dissipate as much heat as brake discs normally do, which can get red hot in no time in a fun roadster. At full rate deceleration with ABS, i would think the power output by the motor would be in tens of kilowatts, thats a big freaking furnace.

Timo

1:54am | Jul 2, 2007

How about this:

Regen braking could use a slider which transfers regen from accelerator to brakes and back, so that you still get full regen braking and could get "coasting" or you could get strong "engine braking" if you like that.

AFAIK Tesla Roadster doesn't use regen braking at all for brake pedal, it is normal friction brake. That could be changed for Whitestar.

Also, if batteries are full I would not like brakes or accelerator to behave any differently, so that resistor-pack to prevent excess charging would really be pretty much necessity.

It seems to me it would be totally fine if lifting off caused maximum regen. A certain accelerator position will still correspond to "coasting". I still think it would be handy to have some visual feedback to show you how much positive or negative torque your foot is requesting. Maybe also adding an "economy" option would be cool, so you really have to plant your foot to empty the battery.

I also would vote against too many user adjustments or "configuration settings". It's just a needless complication and something that I would probably manage to mess up. (Or worse, a reviewer might mess it up and then blame the car and give a bad review. I've seen this happen with, for example, digital cameras.)

I would prefer to keep it simple and let Tesla's engineers figure this stuff out -- I don't want to do their job. However, I may be biased since I am a Mac user. I figure the guys asking for configuration settings are heavy into Linux. :D

James Merritt wrote, why not have performance profiles to simulate different cars? I think it's a bad idea. Even if it were possible (of which I have some doubts), shouldn't the Roadster have its own identity, its own personality? It should be programmed, in firmware, to be the best sports car that its physical parameters allow.

DGP

5:49am | Jul 2, 2007

as for regen braking with a full battery charge: why not just send the excess power to both the heater and the AC? operating the vehicle with a full charge should only last a short time anyway and simple solutions might be appropriate.

Although informative I have questions about it. How effective is the regenerative braking? Could you verify that Tesla has a load resistor that is used by the re-gen system on some conditions?

What is the minimum time & distance to stop from 60 mph with
a) full re-gen and brakes,
b) re-gen only with load resistor,
c) re-gen only without load resistor,
d) re-gen only with load resistor and control set to coast below 3 mph.

I cannot imagine anyone actually choosing to have re-gen cut out below 3 mph. Why? I can imagine that it does not make much difference and that is why I would like to see the last performance spec. d. Another possibility with electric cars is to apply braking power by switching to reverse before coming to a complete stop. This would consume energy and I would request that this mode is not used in the above tests. The difference between stopping distance using the load resistor and re-gen only would indicate in a non-quantitative manner how efficient the re-gen braking is.

A lot of readers have mentioned this load resistor, I believe that the Roadster has one and yes it can be used when the battery pack is fully charged. Load resistors do not wear out.

Joseph: I agree with your comments on re-gen but not the marketing of Whitestars. Prototypes are very expensive and there are many previous blog issues describing the extensive testing that Tesla does. Average users would never give as much useable information for the design engineers.

# Tony Belding wrote on July 2nd, 2007 at 5:23 am
## I also would vote against too many user adjustments or “configuration settings”.
## I would prefer to keep it simple and let Tesla’s engineers figure this stuff out

As much as I would like full control over everything, I realize that keeping the controls simple is a good idea for most drivers. Still if you look around at cars these days, there do tend to be a few more controls than what we used to expect.
On my IS300 there are these buttons:
* Traction control on/off
* Transmission programming for "snow mode", "regular" or "sport mode".
On some cars there are suspension settings like soft / firm or comfort / sport.
So, I don't think it is out of the question to offer a few "profiles" to pick from even if they don't offer full adjustability.
(Perhaps even just a button for "regular" vs "heavy" regen)

When I looked at all the controls and readouts on the AC-Propulsion eBox I thought "way too geeky".
They have the fully adjustable regen slider, and a low-res monochrome LCD dashboard display with way too many details in bland looking text.
Tesla at least has their "mult-function display" off to the side, with nice looking color charts rather than simply a data terminal.
Things in front of you do need to be easy to understand and pleasing to the eyes.
I hope Tesla makes the Whitestar dashboard a good compromise for all types of drivers.

Some reviews of the AC-propulsion cars say that people soon get used to turning up the regen slider and using the "torque pedal" for most of their driving. They basically use the brake pedal only for emergency stops. It would be a shame if Tesla didn't have some way to provide this new driving paradigm for those who would get used to it and want it.

Pete

10:14am | Jul 2, 2007

I think the balance blog post is a little overused by the editor; it is not really an "answer all" post with regards to energy storage. In any case the idea of using capacitors to store regen makes a lot of sense and capacitors are not exactly a newfangled technology (first developed in 1745!). Another option is to just push the current through a resistor. I don't think it makes sense to have an inconsistent profile for regen based on the battery state. A driver expects the breaking behavior of a vehicle to remain constant regardless of the battery charge levels.

James Anderson Merritt

10:51am | Jul 2, 2007

# Tony Belding wrote

# James Merritt wrote, why not have performance profiles to simulate different
# cars? I think it’s a bad idea. Even if it were possible (of which I have some
# doubts), shouldn’t the Roadster have its own identity, its own personality?
# It should be programmed, in firmware, to be the best sports car that its
# physical parameters allow.

I don't mind you calling my ideas bad. But please criticize my actual ideas. First, I didn't say that the Tesla should only imitate other cars. I specifically mentioned that the "mimic" settings would be in addition to Tesla's own unique, optimized profiles. Second, I didn't say that the Tesla should mimic other cars "just because." Rather, I said that the mimic profiles (I envisioned only a handful of them) should be chosen because the car in question has potentially preferable behavior in some circumstances, a particular "engine braking" response, for instance. In other words, the driver should get something important for making the choice, over and above the "driving feel" of some other car. And I certainly don't think any mimicry would be complete. For one thing, a lot of other cars' performance characteristics hinge on skillful and timely gear-shifting, which the Tesla would not offer. Perhaps a mimic profile might help a driver initially be more comfortable, who was used to a particular kind of car in a particular situation he or she encountered routinely.

Personally, I probably wouldn't use mimic profiles except to satisfy my own curiosity, just as I now rarely employ more than a couple of "acoustic profiles" on my audio amplifier. But I can imagine that others might, although the response to the idea in this forum suggests that I might be "overimagining." ;-)

diego

12:46pm | Jul 2, 2007

There's already an UK electric car company using better bateries (way better) than the Tesla roadster, they have also built a sport electric car rated at 700HP.

The battery company is called Altairnano, based in Reno, Nevada, here are some specs from the batteries
# Three times the power of existing batteries
# A one-minute recharge
# High cycle life—10,000 to 15,000 charges vs. 750 for existing batteries
# The capability to operate in extreme temperatures:
-22° to 480° Fahrenheit
# Low life-cycle costs

My son just finished a week-end at infineon race track where he is in the process of developing his driving skills and his car to campaign on the track. The car is a mildly-modified, well balanced '85 Mercedes 190E-16 Valve. I wonder if your Tesla Roadster has run the track and if so, do you have any quantitative data and/or feedback from a good driver for comparison.

During one of the meetings after a driving session, the subject of running the Tesla Roadster was discussed and someone in the group said the Tesla couldn't be run at sustained all out track speeds without the battery exploding. How true is that?

I love the Roadster's design and think if it is a track-proven car, that would be a definite plus for the car.

I am fortunate to have driven a number of EV's with Regen for many years. So I hope I can provide some useful comments here.

First of all, thank you Greg for a excellent description of how it all works.

It's good to see the later comments mentioning the drawbacks of adjustable regen. The truth is, if you are used to having the regen strength knob "here" and suddenly it is "there" the car feels very different. This can be a rude shock on a mountain road or for a different friver of the car. It is not that hard to make the brakes feel smooth when transitioning from regen to friction so I expect that is what Tesla will do. If you find you want more regen efficiency the simple solution is to learn to feel for that slight change of the addition of friction braking when pushing the brake pedal and avoid friction braking for regular driving.

As for dissipating energy electrically, I don't think it's worth the weight. The Roadster has more than adequate brakes for any mountain decent. I believe they will dissipate any rare extra energy while creating much less dead weight than a resistor bank would. And of course if super caps were any good for storing energy, we'd use them instead of batteries. (hint, they are not that good as of today)

Some people who are used to driving with one foot might like stronger regen on the accelerator pedal (but woe to those who try to coast in this mode!). Given time, I suspect the hacking community will find a way to do that and by their modifications hopefully release Tesla from the potential liability of such a mod while the rest of us drive a nice predictable and safe car.

-Otmar

Malcolm Wilson

11:56pm | Jul 2, 2007

# Roy wrote
# Average users would never give as much useable information for the design engineers.

Other than information on the driving habits and recharging behaviour of average users. Some of that will be sports car-specific, but other details gleaned from the hundreds of charge/recharge cycles and hundreds of thousands of road miles covered will be very useful for the next vehicles. Helps Tesla build up a profile of a typical Roadster/EV user.

I know that the PEM stores data on charge/recharge cycles which can be accessed and downloaded by Tesla service engineers. Makes sense. The ESS is the critical technology in Tesla's business. I don't think there's a tachograph system which records the relative use of regen versus mechanical braking. Probably because these are integral to the feel of the drive and braking behaviour in particular, is governed by safety regs. You wouldn't want customers to adjust that, anymore than you'd want them to stick spoilers on the bodywork.

If Tesla does provide adjustable regen and acceleration profiles then they should be in the form of pre-sets. A handful of company tested and certified downloads for the PEM. But to be honest I don't think the average motorist would notice much difference other than the most obvious ones - longer 0 to 60 times, better milage etc. But you don't really need new software for that - just a gentler right foot.

It's a tough call. From what i've been reading, Tesla could make the Roadster an even more extraordinary driving experience - but at the risk of alienating an ICE-familiar public. So at present, they are sticking to emphasising EV behaviours which match the Roadster's target market - high torque for sports car enthusiasts. Maybe later models can highlight other unique EV behaviours.

Michael

4:05am | Jul 3, 2007

I strongly believe it would be in our/Tesla interest to link regen strength to brake pressure instead of having only friction braking. Seems like at the minimum, it would allow some additional energy recapture, which has no downside up to the point in which total battery capacity is reached.

Although it could be said that people should quickly be able to get used to a different driving dynamic, it should be recognized that having this different driving dynamic as an option would be better than scaring people off that try to test drive the vehicle and the change is too dramatic for them to feel comfortable in the short time they would have to get used to the vehicle.

Brent

6:56am | Jul 3, 2007

#Isaac Ladson asks...
#During one of the meetings after a driving session, the subject of running the Tesla Roadster was discussed and someone in the #group said the Tesla couldn’t be run at sustained all out track speeds without the battery exploding. How true is that?

Maybe if the batteries exploded just so, you could get a bit of extra thrust out of them. ;-)

TM has so far kept quiet about how far you'll be able to go at 130 MPH, the car's top speed, but some people have estimated a max distance of about 60 miles, or less than 30 minutes of driving. The batteries might get hot, but there's no reason to think they'd actually burst into flame. The power output levels at that speed are well within the batteries' discharge profile.

Brent

7:07am | Jul 3, 2007

#diego wrote on July 2nd, 2007 at 1:46 pm
#There’s already an UK electric car company using better bateries (way better) than the Tesla roadster, they have also built a sport #electric car rated at 700HP.

These batteries have been thorougly discussed on previous blog entries. Whether they're better or not depends on your perspective. One thing is certain: they're expensive. The UK car has an estimated price of $300,000.

The Roadster has been often criticized for being for the "rich" only, but its price is still within the range that the "ordinary rich" might buy.

AMonteiro

7:54am | Jul 3, 2007

I think about regenerative braking since I started thinking about EVs (some four years ago). Now I drive a conventional car with automatic gear that allows also sequential changes.

In this last configuration which I use sometimes for speed reduction (of course without energy recovery) I keep thinking it would be wonderful to have a continuous slider with the following functionality:

- When fully forward, when you lift the accelerator pedal totally, the car would keep running without any speed reduction;
- When fully backwards, when you lift the accelerator pedal totally, the car would have maximum speed reduction (regenerative);
- In the intermediate positions it would have intermediate speed reduction (regenerative).

With this functionality, you would have the option to leave the slider in a constant position for zero or relatively low reduction; or relatively high reduction for a more nervous driving; or keep changing it according to the momentary situation.

I notice that in many situations it would be nice to let the car go just with its own inertia, without having to keep the pressure on the pedal. But in the next moment, we needed a progressive speed reduction. It would be comfortable to pull back a little slider and get the reduction without braking. This happens a lot within traffic.

I don't think that it is dangerous. It is not that different from a gearbox that you have to control (with a much more complex procedure) to get the right speed reduction.

Brandon

9:58am | Jul 3, 2007

Diego: "Magical New Components: Someone has always 'just come out with' a magic motor, a better battery, or some other holy grail that will give you amazing range and power, weighs almost nothing, produces more power than it uses and cures cancer. On closer inspection, you will find that these fantasy components are hand-built laboratory prototypes. They also have a few drawbacks, like enormous price tags, 600F operating temperatures, or a tenancy to self-destruct. Someday some of these fairy tales will come true and will benefit us all. In the meantime, it is foolish to base your vehicle on the magic of tomorrow. If you do, your dream coach-and-four will remain a lumpy pumpkin pulled by white mice. Build with available technology today. You can always upgrade later." From Convert it, by Michael P. Brown and Shari Prange. I think Tesla lives by a similar philosophy and I applaud them for it.

# Otmar wrote on July 3rd, 2007 at 12:14 am
## Some people who are used to driving with one foot might like stronger regen on the accelerator pedal.

Yep... So I suggested a simple button for two settings - normal vs heavy regen.

## I suspect the hacking community will find a way to do that and by their modifications hopefully release Tesla from the potential liability

That brings up an interesting point - just how far does a company have to go (to prevent the aftermarket from making a change) to keep themselves from being liable.
With the Toyota NAV system for instance it doesn't let you enter destinations while in motion, so the driver won't be distracted by the GPS and get in an accident. People found that you could press a magic sequence on the display to unlock it. The following year, Toyota updated the software and made a new secret sequence that again leaked out. If Tesla were to provide a backdoor on the VDS that let you adjust regen, and never publicly announced it, but it leaked out as a diagnostic feature that was theoretically only for internal factory use would that absolve them from responsibility?
People also found out that you can play video DVDs on the Toyota NAV system if you open the dash and put a jumper on one of the connectors. Is that too much of an "attractive nuisance" that they made it easy to enable that feature with just a screwdriver and piece of wire?
I see the same thing with home DVR devices. Many have a 30 second commercial skip feature that is disabled by default unless you ask the "right person" and they tell you how to activate it after you get home.

I suppose Tesla could go a whole range from engineering in anti-tampering measures, to publishing schematics with extra "test points" already engineered in to make it easier for outsiders to make modifications.

By the way, thanks for stopping by, Otmar... It is good to see you here finally!

Mark W.

6:15pm | Jul 3, 2007

If I understand things correctly, each driver has a profile stored in the computer that is activated through an access code (needed to start the car). If the amount of regen was controlled in this manner, I think this would solve most of the problem of adjustable regen. I assume the the car also has a guest mode that could be used for reviewer, thus solving the problem of someone driving the car that is unfamiliar with it (use factory defaults)

Tony Clevenger

9:37pm | Jul 3, 2007

I understand the regen braking but, have you thought of using linear voltage generators ? i'm sure these can be used alone, or in tandem with your shock absorbers .This would not only make your ride totally adjustable, but would also give back a sustantial voltage and current to be used in your battery or propulsion.

But Roy, the gyroscopic effect on handling has already been solved by the aviation industry. So your car will want to spin in the opposite direction to the flywheel whenever you tap the break pedal. So just do what they do in helicopters and mount a giant sideways-facing propeller on a boom protruding from the back of the car, blowing air into the direction of spin. Presto, gyroscopic forces are cancelled out.

I mean, duh.

Richard Connamacher

10:25pm | Jul 3, 2007

In all seriousness, I love how Tesla has made a conscious decision to stick with the sorts of proven technology available today. The Roadster is a great testament to what is already available but nobody has had the forethought to provide: the batteries we already have, the motor mechanisms we already have, the physical materials we already have, and the car body designs we already have.

This isn't meant to diminish the incredible amount of R&D I'm sure Tesla has put into this car. Just because the raw materials are all proven technologies doesn't mean that putting them together is easy. The ESS and Tesla's brushless motor both look to be incredible feats of engineering that I'm sure have been heavily patented.

This point is extra sweet, considering that just a couple of years ago major automakers were saying that the reason electric cars aren't viable is because battery technology just isn't there yet. Tesla is busy proving them wrong, and they're using last year's proven Li-Ion cells to do it. Kudos!

If integrating ultracaps into the ESS as a temporary energy buffer will improve the car's efficiency, then I'm sure Tesla's engineers will look into it. But the point is, cutting-edge or future technology isn't actually *needed* for a shipping car -- and what we need is a car to ship this year. Enhancements and experimentation with new tech can come later

Timo

5:31am | Jul 4, 2007

# diego wrote on July 2nd, 2007 at 1:46 pm

# There’s already an UK electric car company using better
# bateries (way better) than the Tesla roadster, they have also built
# a sport electric car rated at 700HP.

# The battery company is called Altairnano, based in Reno, Nevada,

Altairnano is old news to these blogs. The reason why Tesla isn't using them is:

a) They are expensive
b) They are expensive
c) They have lower energy density than Tesla batteries (about 30% lower than Tesla)
d) They can't (yet) produce big enough volume of those batteries to meet the requirement.

But technically they are better than Tesla batteries. You are right about that. I bet Tesla will start to use them or A123 batteries (or similar) in near future once those companies get their prices down, or that tech becomes available to Tesla without third party in a way.

BTW which car are you talking about? UK has one called Lightning. Is that the one? That one uses hub-motors and you should look at feel-blog "Driving Dynamics - Part 2" why Tesla doesn't. Hub motors without friction brakes is, I believe, also not road-legal in US, so no US-market for them. And it might be that several European countries have this same restriction.

They might get fist of those done by 2009. I bet by that time Telsa has already sold tens of thousands of cars, both Whitestar and Roadster.

And Telsa Roadster is much better looking car :-).

diego

9:02am | Jul 4, 2007

Yes I was talking about the Lightning ($295.000). I dunno that much about all these batteries or which electric motor is better. The Altairnano batteries sound interesting even if they still need work.
I'm hoping that the Tesla people rethink the Whitestar name, it sounds like a kitchen appliance to me, it needs a more up-to-date and catchy name, for example look at the Honda Fit (or Jazz in Europe) the name is catchy and sounds like fun, but hey that's just my opinion.
BTW China is also building small electric vehicles so I will buy the first one that gets over here (Costa Rica) even if it's chinese.

Timo

1:36pm | Jul 4, 2007

# diego wrote on July 4th, 2007 at 10:02 am

# I’m hoping that the Tesla people rethink the Whitestar name,
# it sounds like a kitchen appliance to me, it needs a more up-to-date
# and catchy name,

Don't worry, that is just working codename. Roadster was "Dark Star".

Richard Connamacher

4:14pm | Jul 4, 2007

Diego: As far as I know, the Whitestar is just a development codename. If I remember right, the codename for the Roadster was Darkstar or something like it. I'm sure there'll be a new name whenever it's officially unveiled (2009 or so)

TEG2 - The Empire Strikes Back in Black

5:01pm | Jul 4, 2007

# diego wrote on July 4th, 2007 at 10:02 am
## I’m hoping that the Tesla people rethink the Whitestar name

That is just an internal code-name that has become a bit too public. I don't think they ever intended to call the final model by that name.

For instance, the "Roadster" was code-named "DarkStar" during early development.

Maybe Tesla simply calls Model2 the "Tesla Sedan" to go along with "The Roadster"?

## BTW China is also building small electric vehicles so I will buy the first one that gets over here

I am too against a selector of regen, purely for safety reasons. I am sure it would be intersting feature for certain occasions. I explain why I think it would be unsafe. During last 10 days I had to drive 3 different cars on my daily way to work because mine is in garage. Each car had different brakes, some stronger, some weaker. Very bad feeling when the car is decelerating at different rate than one is used to. Can create dangerous situations. To change settings of a machine instantly is no problem, to change "settings" of human body is a different story. Should not be forgotten that brakes are there to safely stop the car in the first place, and if it does regen in the process is just a bonus.

Zythryn

7:48am | Jul 5, 2007

"I’m hoping that the Tesla people rethink the Whitestar name, it sounds like a kitchen appliance to me, it needs a more up-to-date and catchy name, for example look at the Honda Fit "

Diego, I really hope you are joking:) The Honda Fit is a name that instantly makes me think of the 80s and fitness videos (not a thought I want in my head.
The Whitestar is the perfect name in my opinion. Brings to mind Babylon 5 =o)

The name "whitestar' is just being used in developement. The Roadster was called the darkstar when it was at the same point in developement. Nobody expects that name to last even to the first prototypes.

Robert

12:45pm | Jul 5, 2007

Is there any concept drawings of the WhiteStar coming out soon?

Nubo

2:51pm | Jul 5, 2007

First, as long as the conventional brake system is good, no worries.

As pointed out, potential for over-filling batteries is going to be rare. If you're coming down a big hill chances are you've either climbed a big hill, or driven some miles to get there. In most cases regen is going to be less than energy already spent. In those rare cases where regen has to disengage, the concern is that it be done smoothly and safely. But there is no reason to worry about brake wear for such a rare occurance.

When applying brakes, whatever contribution regen can make should be made. When "coasting", the default should approximate engine-braking of a "normal" car. But, it would be very nice to be able to adjust that default rate. It seems to me that could be done via a "trim wheel". Anyone who's learned to fly will be familiar with how this works. Basically, you adjust the trim wheel so that the plane flies level with a minimum of control input. When you change from cruise to descent, you adjust the wheel again to maintain the new attitude. It's not a substitute for the main controls, it just keeps you from having to constantly pull on them. It's quite easy to get used to. It would be very nice to have something like this in a car while we're descending this proverbial 2000 foot elevation. In a gasoline car, even with manual shifting, one is rarely able to find an equilibrium between acceleration down the hill and engine braking. But with adjustable regen "trim wheel", you could set it exactly right -- getting the most convenient descent and also maximum recharge for the batteries. It's win-win. And during "normal" driving you could set the "engine braking" to match your taste and the situation.

## "the vast majority of the kinetic energy is converted into heat by your brake pads when you stomp on the brakes. "

## "there are some who would prefer ... the regen to be tied to the application of the brake pedal."

So are you saying that Roadster regen is only tied to eMotor coast down, and when you step on the brake pedal it doesn't add any extra regen?

Wouldn't that be wasting a lot of "recapture energy" that you could otherwise get by increasing the regen (when the brake pedal is pushed) rather than always using the friction brakes?

If you don't actually turn on regen based on the brake pedal use this seems like an area that would be ripe for enhancement to get you back to the 250mile range Tesla wants so badly to offer.

It sure does seem like you were hoping not to connect into the brake pedal with your regen based on comments here:http://gizmodo.com/commenter/mharrigan/
"The Tesla Roadster has regenerative braking but it works differently than the typical hybrid. Hybrids apply regen braking when the driver steps on the brake pedal. The Tesla Roadster applies variable regen braking based on accelerator position."

If you had more time and resources to test a brake pedal integrated regen system would you do it?

Isaac Ladson

6:19pm | Jul 5, 2007

Brent:
Thank you for the information. And, I'm sure one day someone will push it on the track to see what happens. I suspect with a few modifications, it will "move like stink."

I have complete faith in TM's engineering, and management, because I see not only innovation but a practical approach to production. There have been many dreams and vapor in developing a mass market BEV and outside entities with other agendas, intent on slowing down the progress. Currently the entrenched auto companies are still pushing ICEs but with the new twist of using "clean, sure it is, diesel."

Steven

6:29pm | Jul 5, 2007

You mention that regenerative braking has to be stopped/limited when the batteries are fully charged. But, especially given the theoretical 64% maximum regeneration, under what circumstances would this situation realistically arrive? Descending a hill after having charged your battery at the top I guess?

And Richard, what I never understood about the big carmakers poo-pooing electric cars for lack of a good enough battery was how strongly they've embraced the dream of hydrogen fuel cell at the same time. Because how does a hydrogen fuel cell power a car? With an electric motor of course!! Wouldn't it be smart for them to get a jumpstart on all the other engineering that goes into an electric car so that when their magical pipe dream comes true they'll have a fittingly refined car to make use of it?

Michael

1:26am | Jul 6, 2007

Is the plan for the Whitestar to have brake initiated regen? If not, please consider this. It seems like it would be the most important step in energy recovery for increasing range.

James Anderson Merritt

10:39am | Jul 6, 2007

# diego wrote on July 4th, 2007 at 10:02 am

# BTW China is also building small electric vehicles

I believe that the 40MPH & 40 MPR (miles per recharge) ZAP Xebra is made in China. I don't know about the import and roadworthiness requirements in Costa Rica, but if your aim is zero-emissions, low cost-per-mile transportation, as opposed to the blazing speed and handling of something like a Tesla Roadster, the Xebra could be for you. They have both a sedan and a pick-up truck model; you might find the latter of more use if you live in the more rural areas of CR.

Mark Higley's video shows quick shots of sedans and pick-ups as customized by their owners, and is especially informative about the construction and appointments of the pick-up model. (It's also rather well produced, in my opinion). Other videos take you along for test drives, show the vehicles in action, etc.

As much as I long for the Roadster and Whitestar, if a Xebra could do 70-80 on the freeway and travel 100-120 miles per day -- or if I had a job in my own home town and didn't have to commute over a mountain highway every day -- I'd seriously consider one. I figure that a model capable of what I need might run up to $20000-25000. But the current model is sold for between $10000-15000, which seems like a pretty good deal for a "city car."

Hydraulic regen is pretty neat too. Not that it would be useful on an BEV at all, but for larger ICE vehicles it makes for a simpler way to recapture energy. It would be swell if say the EPA liscenesed some sort of Hydraulic Launch Assist technology to a company such as Ford for a possible 2010 60 mpg(city) F150.

:-)

Pete

3:54pm | Jul 6, 2007

It would be great if Greg Solberg could chime in a clear the air with regards to regen. Judging buy the posts so far people are not very clear on the interop between the mechanical breaks and regen or what triggers regen. Thanks for any insight you can offer.

Richard Connamacher

6:02pm | Jul 6, 2007

Mark Tebbutt:

# A tiny generator powered by natural vibrations...

Assuming you are talking only about recapturing a portion of the car's energy lost to friction for a modest improvement in range (and not a perpetual motion machine using its own vibration a source of power -- in which case I would tell you to go read up on your Physics a bit more), I don't think an invention like that would do a whole lot in a car like the Roadster.

Keep in mind, the only source of vibration on the Roadster would be road friction, as its engine has no pistons bouncing back and forth like iCEs do.

Theoretically, if a vibration electric generator were used, it'd be in addition to shock absorbers in the same way regenerative braking is used in addition to regular friction brakes. And, its purpose would be to reduce the energy losses due to road friction in the same way regen recovers some of the energy lost from stop-and-go traffic. It wouldn't supply energy on its own, just somewhat reduce the losses from driving on a very bumpy road.

Now, I haven't looked into their generator, so I may not know what I'm talking about. But something tells me that its modest boost to range is not going to be nearly good enough for the weight, complexity, and massive amount of R&D required (their microwatt invention isn't exactly road-worthy) to turn this into a regenerative shock absorber.

But then again, maybe some engineer will come along and prove me wrong.

Richard Connamacher

6:39pm | Jul 6, 2007

Steven:

My thoughts exactly!

In the recent words of Bill Clinton, our current energy infrastructure is facing a shift from a centralized model to a decentralized model, and established business has been doing a fine job making money with our existing centralized economy and see no need to change.

Gas and diesel cars are powered by a massively centralized infrastructure. Electric cars are the exact opposite end of the spectrum, powered by any number of energy sources including their owners own rooftops.

I think that both automakers and oil companies see hydrogen-powered cars as a somewhat less centralized, but still centralized, energy economy. There's still money to be made in the "refining" (manufacturing) and delivery of fuel there. And, as a realistically useful hydrogen infrstructure is years (if not decades) and billions of dollars away, automakers can continue selling their existing gasoline powered cars today. Why throw out the hundred years of expensive R&D that they've spent making today's gasoline and diesel cars if they don't have to?

Richard Connamacher

6:50pm | Jul 6, 2007

Isaac Ladson:

I for one am happy about "clean"er diesel. If it reduces the amount of smog in the air due to better carbon filters (which the sulfer was tearing up before), and reduces the amount of oil our country has to import and burn to drive around (as diesel is much more fuel efficient than gasoline), then I'm all for it. Sure, it's not zero emmission, but it's a step in the right direction. Not the same as what Tesla's doing, but useful for those who still have needs beyond what battery electric ars like the Tesla can provide. (Namely, long trip capability.)

As a stepping stone towards a true electric car economy, I think diesel-electric hybrids make a hell of a lot more sense than hydrogen or "flex fuel" cars. Now we just need to get some consumer diesel-electric hybrids on the market!

And, keep in mind that it'll be quite some time before cross country truckers start using electric vehicles. A major storage and charging speed breakthrough would have to happen before they'd even consider it -- and highway charging stations would have to become as common as diesel truck stops are today. If clean diesel means less soot from semis, that's a good thing in my book.

CM

7:50pm | Jul 6, 2007

Merrit, the Xebra won't meet your performance needs. The Zap Xebra is a "neigborhood electric vehicle" with a top speed of 40 mph and a range of 25 miles. See Zapworld.com for more details.

Zap is planning to offer longer range freeway capable electric vehicles sometime in the future (Zap-X, Obvio 828E, Obvio 012E, and an unnamed model), but they are still in the early planning stages. I suspect Tesla models #2 and #3 may be a bit closer to production.

Mark Tomlinson

9:29pm | Jul 6, 2007

Pete (and others), I thought Greg was pretty clear.
** Since regen is ineffective below 2-3 MPH, and regulations require friction brakes for safety, you can bet that the friction brakes will have to be used at near walking speed. Regen will be active right down to that point.
** There won't be an clear line where regen braking stops and friction braking begins based on his comments about safety. If the car ahead of me suddenly stops, I don't want to depend on aggressive regen. It all depends on the specific stopping situation.
** It's well known (through Greg's comments, interviews, and other blogs) that regen begins when we let up on the accelerator and continues through pushing the brake pedal. This will allow the "engine braking" effect that lets us regen while coasting downhill.
** An earlier blog (by Martin?) suggested that the brake lights will go on when regen slows the car sufficiently - even if we don't touch the brake.
** So regen braking and friction braking appear to be independent of each other - with the possible exception that putting your foot on the brake MAY switch to aggressive regen. I don't recall that Greg was clear on that point.

Mark Tomlinson

9:59pm | Jul 6, 2007

My personal torque profile preference:
(1) Regen increases over time. I don't want slight variations in the accelerator position to lurch the car into regen. But if I change the position of the accelerator for more than a fraction of a second, I'd want regen to "ramp up" to the appropriate level.
(2) Regen depends on speed versus accelerator position. When traveling at a high speed, I'd like less aggressive regen to prevent rapid deceleration. (This may accomplish my first point since regen would increase as the car slows).
(3) The brake pedal operates opposite of the accelerator. Okay, sounds like a stupid comment. But what I mean is that the further down you put the accelerator, the more power goes to the motor/generator. So the further down I put the brake pedal, the more power I'd expect is allowed to come from the motor/generator.
(4) The friction brakes are adjusted to allow for regen. The combination of regen and friction brakes should not bring the car to an unintended screeching stop. Other than that, I see no reason to marry the two. I would expect that the friction brakes, ABS and all, are intended for stopping - not slowing.

Joseph

10:01pm | Jul 6, 2007

I'm confused.

Some of you are saying that the regen is related to the accelerator position and/or that the brake pedal only operates the friction brakes, not regen. Neither makes any sense to me.

#TEG2 wrote:
##Wouldn’t that be wasting a lot of “recapture energy” that you could otherwise get by increasing the regen
##(when the brake pedal is pushed) rather than always using the friction brakes?

Not if the regen level with your foot off the accelerator is already at maximum.

That is so cool. I can't wait to more affordable Tesla vehicles. I will be first in line.

Anatoly Moskalev

11:27am | Jul 7, 2007

To Pete:

As I remember it was explained once in some blog that regen is activated only by acceleration pedal. Brake pedal controls only usual friction brakes. It is not very clear how requested torque is determined by the position of brake pedal. This requires clarifications from Tesla Motors team.
I think in general torque is some function of vehicle velocity (basically RPM of eMotor) and position of acceleration pedal. Extra limitations comes from algorithms preventing rear wheels slip versus road surface and from battery not capable to store coming from regen energy. Goind down hill with fully charged battery is basically the only case of battery not capable to store regen energy. This should be fairly rare case.
Assuming no extra limitations of torque by mentioned algorithms torque would monotonically increase by heavier push of accelerator pedal. But it should also be a negative torque factor added increasing with velocity (RPM). So it will exist a position of acceleration pedal for a given velocity corresponding to zero torque. The higher the velocity the deeper driver have to push acceleration pedal to make zero torque.
So regen automatically come into play if for a given velocity accelerator pedal is not pushed deep enough. Intensity of regen would be controlled by how much driver released acceleration pedal versus zero torque position corresponding to velocity. For a fixed road conditions if driver pushed accelerator pedal to some level and fix it there car would accelerate and at some velocity it would start losing torque because position of zero torque for accelerator pedal would come close enough behing maintained accelerator pedal position. So at some point reducing torque would match resistance forces for a given velocity. From that point car would just keep that velocity. If resistance would increase because of road conditions change velocity would somewhat drop and torque grow to match new equilibrium velocity.

Now if driver release accelerator pedal sufficiently (not nesessarily to release completely) negative torque factor from velocity would exceed positive torque factor from new pedal position. So eMotor controller would instantly get negative torque command and apply it. Car would start losing speed quickly and regenerating energy back to ESS in the process. By losing speed negative torque factor would reduce and at some point growing torque would macth resistance forces for car moving at particular speed at which this match happen. From that position car would move at new equilibrium speed.

Overall result of described negative feedback loop versus velocity would manage car matching speed to accelerator pedal position. Heavy regen starts by dropping acceleration pedal completely and in such case I think equlibrium speed disabling regen would be zero or close to zero. If you also push brake pedal after dropping accelerator pedal you would get extra deseleration from friction brakes so regen brake and friction brake would act in parallel helping each other to stop the car.
So if driver frequently uses brake pedal regen braking will capture very limited energy. Anyway with normal driving style people always use single foot between acceleration and brake pedal. By releasing acceleration pedal driver already get full regen braking applied. It also would be much more intense than ICE engine brake in high gear. Overall effect would be like in normal ICE engine car instantly coming to lowest gear. After that pushing brake pedal would just increase braking. If you do not need very sharp speed loss you just do not touch brake pedal and car would reduce speed completely by regen by just releasing somewhat or fully acceleration pedal. It would come to complete stop by itself if driver remove feets from pedals completely.

Under described overall priciple it exist infinite variability of how exactly torque increases and reduces versus velocity and acceleration pedal position. Heavy regen implies high negative torque applied by fairly small shift back of acceleration pedal. At this limit car velocity basically follows closely angle of push of accelerator pedal. Some people like it as high degree of control how car moves. It surely improves how fast car changes speed in response to driver. Some people like me used to drive low end cars expect it to coast almost freely by releasing acceleration pedal. This would be extreme low regen mode. Discussion here is about is it worth to provide extra end user choice and in what form of control by end user to go between these two extremes of regen.

By my recent work I was exposed to design controllers for printing machines and other electronics using eMotors in fancy movements. From that point of view I am very familiar with implementation details of what would be used in any EV. Key differnece between what I know and what Tesla Motors is using is power level at what this all happens. I am used to much lower power but fancier (but also slower) movements of simple robotic systems compared to EV.

Richard

6:57am | Jul 8, 2007

If you take your foot off the throttle pedal, put it on, take it off, put it on, take it off, etcetera, energy will be converted from kinetic to potential many times, with only about 80% efficiency. That is an extremely inefficient use of energy.

Cars should coast when you take your foot off the accelerator pedal. Bringing it to a stop is what the brake pedal is meant to do. Anything else is simply an illogical design of the vehicle's interface and an inefficient usage of energy.

Richard

7:08am | Jul 8, 2007

I made a mistake in my post. I meant to say:

"If you take your foot off the throttle pedal, put it on, take it off, put it on, take it off, etcetera, energy will be converted from kinetic to potential many times, with only about 80% efficiency each time"

By the way, although I did not state it clearly in my previous post, I will state it clearly now. The regenerative braking in the Tesla Roadster should function as it does in the Toyota Prius. Therefore, it should only be applied when the brake pedal is pressed and it should maximize the amount of energy that is regenerated by minimizing the use of the brake pads (this should have the side benefit of making the brake pads last the life of the vehicle). It should not operate when the driver's foot is taken off the accelerator.

diego

7:31am | Jul 8, 2007

Yes I plan to use it for city driving, the other day a friend of mine passed me a link to another car designed by Lotus and Zap which is a 644HP five seater and I think they are using also the Altairnano titanium batteries and looks that they are taking orders, but for now I will wait for the smart fortwo cdi hybdrid.

James Anderson Merritt

4:19pm | Jul 8, 2007

# diego wrote on July 8th, 2007 at 8:31 am

# Yes I plan to use it for city driving, the other day a friend of mine passed
# me a link to another car designed by Lotus and Zap which is a 644HP
# five seater and I think they are using also the Altairnano titanium batteries
# and looks that they are taking orders, but for now I will wait for the smart
# fortwo cdi hybdrid.

As far as I know, the Xebra car, with several hundred sold so far, is the only production EV that ZAP will actually be delivering in the next year or so. They may surprise me: I read in the San Jose Mercury-News today that the EV version of the Brazilian Obvio was slated to come to market in 2008 under the ZAP umbrella. If so, wonderful, as it sounds like an exciting car. But they've been talking about this one (and perhaps even taking orders/reservations) for quite a while, so I will believe it when I see it. In the meantime, the Xebra is the only "real" vehicle they have. At this time last year, there was talk about how the Xebra would optionally be available with NiMH or Lithium batteries to provide extra range and/or oomph for hills, etc. But a year has passed and the Xebra still seems to use gel lead-acid batteries. It looks as if ZAP is serious about delivering real vehicles, but their substantive improvement and line extension is taking place more slowly than their production of hype. Of course, to keep things in perspective: we are still waiting on Tesla to deliver the Roadster in substantial numbers at all. This time last year, there was talk about how Tesla would be putting Roadsters in customer hands by late summer 2007. Here we are, and it appears as if late fall 2007 or early winter 2008 will be closer to the mark. I'm not worried; good technological developments generally take more time than anyone estimates at the start. Tesla will be doing well to deliver around the end of this year. But for us here on the outside, waiting is definitely a form of torture. :-)

By the way, were you aware that the Smart Fortwo was originally scheduled to come to America under the ZAP banner as well? DaimlerChrysler apparently double-crossed ZAP and the credibility problem the latter suffered as a result is a big PR hole they are attempting to escape. In the same SJ Mercury-News article I mentioned above, the ZAP CEO now says the mis-step with the Fortwo was probably a good thing for ZAP in retrospect, as it cleared their decks to concentrate on pure EVs (Xebra, Obvio EV, ZAP-X).

As careful as you should be about trusting the claims and promises of vendors, you should probably be just as careful to establish a "deadline" by when you will purchase your EV, and then get the best value for your money that is available at that time. There will always be a reason to wait "just a little bit longer" for something that is just over the horizon. But until we have some experience with how well various vendors keep their promises and make timely deliveries, rewarding those vendors who have suitable stock on hand when you are in a buying mood seems like the best way to get good value AND encourage the good behavior of the industry in general. At the moment, nobody is selling an EV that meets my needs, or I would be taking my own advice. But once that situation changes, watch out! ;-)

Anatoly: Are you sure? You have assumed that Tesla uses speed control instead of torque control. I for one think that torque control is more desirable for driving a car and would give the gas pedal a feel more like what we are used to. Anyone who has driven a Tesla Roadster could set us straight as the feel would be quite different. If you quickly move the pedal to say 2/3 down then under speed control the rear wheels would spin furiously at about 60mph immediately but under torque control would apply about half the available torque and take off rapidly but with no smoke!

# Mark Tomlinson wrote on July 6th, 2007 at 10:29 pm
## ** So regen braking and friction braking appear to be independent of each other
## - with the possible exception that putting your foot on the brake MAY switch to aggressive regen.
## I don’t recall that Greg was clear on that point.

Yes, that is a big question. Does use of the brake pedal have any influence on the aggressiveness of regen?
At a minimum, without actually tying into the hydraulic system, they could (theoretically) use the pedal switch (which normally would activate the brake lights) to switch to a second mode with more regen. Or they could have a potentiometer/rheostat on the brake pedal to adjust the regen profile to increase in parallel to the friction brakes.

#TEG2 wrote:
##Wouldn’t that be wasting a lot of “recapture energy” that you could otherwise get by increasing the regen
##(when the brake pedal is pushed) rather than always using the friction brakes?
# Steve West replied on July 7th, 2007 at 4:05 am
## Not if the regen level with your foot off the accelerator is already at maximum.

That further refines the question. I gathered from Greg's posting that some people were objecting to the idea of heavy regen simply when you let off the accelerator ("torque") pedal. If you invoke full regen then it can slow you much more quickly than one would be used to from simple engine braking of an ICE car.

Hopefully we find out that they ARE able to use max regen under hard braking and not throw energy at the friction brakes that could otherwise be recaptured by the batteries.

# Anatoly Moskalev wrote on July 7th, 2007 at 12:27 pm
## As I remember it was explained once in some blog that regen is activated only by acceleration pedal.
## Brake pedal controls only usual friction brakes.
## It is not very clear how requested torque is determined by the position of brake pedal.
## This requires clarifications from Tesla Motors team.

Yes, that is what we keep asking.

# Anatoly Moskalev wrote on July 7th, 2007 at 12:27 pm
## So if driver frequently uses brake pedal regen braking will capture very limited energy.

Yes, if letting off the accelerator/"torque" pedal doesn't invoke full regen, and brake pedal doesn't enhance regen then you may be right.
If Tesla is averse to tapping into the brake system to decide on regen amounts another approach would be to use dive/tilt detection. If the vehicle is under heavy braking it would shift more weight onto the front wheels. If you detect that you could bump up regen to help lend a hand and keep some of the burden off the friction brakes. The same system could possibly be used to detect that you were going downhill and so it could enhance regen in those cases. I think it would enhance the driving experience to invoke more regen when going downhill, and reduce the regen when going uphill. It would give the car a sensation of being lighter than its' actual weight.

# Richard wrote on July 8th, 2007 at 7:57 am
## Cars should coast when you take your foot off the accelerator pedal.
## Bringing it to a stop is what the brake pedal is meant to do.
## Anything else is simply an illogical design of the vehicle’s interface and an inefficient usage of energy.

I disagree with that if the brake pedal can't invoke regen first, then transition to friction brakes (when the max regen is insufficient to stop the vehicle fast enough). You could design a vehicle assuming that release of the accelerator pedal would invoke max regen, and then the driver would only use the friction brake pedal when they needed to slow more quickly, but if people insist that release of the accelerator pedal not slow the car so quickly then you may end up using the friction brakes more and regen less which hurts efficiency and heats up ( and wears out ) the brake pads sooner.

# Richard wrote on July 8th, 2007 at 8:08 am
## The regenerative braking in the Tesla Roadster should function as it does in the Toyota Prius.
## Therefore, it should only be applied when the brake pedal is pressed and it should maximize the
## amount of energy that is regenerated by minimizing the use of the brake pads
## (this should have the side benefit of making the brake pads last the life of the vehicle).
## It should not operate when the driver’s foot is taken off the accelerator.

First off, the Prius and other Toyota hybrids do sometimes invoke regen even if you never touch the brake pedal. Also, their transmission selector has a "B" profile which offers enhanced regen when coasting down hills.
But, yes, they do have the eMotor regen tied into use of the brake pedal, and they do offer "off throttle" behavior which can have the car "coast" like you expect from a traditional ICE vehicle.
Tesla had stated that they didn't intend to make the Roadster work this way.

Note these:http://mn.eaaev.org/resources/Tesla%20Presentation%20Notes.pdf
"
• Regen is controlled by removing your foot from the accelerator pedal.
• Regen has 2 levels: Max in low gear, and reduced in high gear (although, it is fully proportional).
• Maximum limits on regen are similar to aggressively down-shifting an ICE sportscar.
• Note that regen is inverse of the drive wheels (i.e. By using the motor, and the car is rear-wheel-drive).
Therefore, because the rear wheels don't provide majority braking,
a maximum of about 80% of the regen opportunity can be realized.
"

http://jalopnik.com/xml/comments/188590
"
The Tesla Roadster has regenerative braking but it works differently than the typical hybrid. Hybrids apply regen braking when the driver steps on the brake pedal. The Tesla Roadster applies variable regen braking based on accelerator position. As the driver eases off the accelerator the regen braking is applied. Regen braking is also a function of the gear selected (2 speed manual gearbox with electric shifing and no clutch). First gear has higher regen braking than second. In driving, it feels very much like a standard transmission gasoline powered car. You can actually come to a complete stop without touching the brake pedal. Also, for those who wonder, the brake lights are computer controlled and based on measured deceleration rather than the standard switch on the brake pedal.
"

Malcolm Wilson

10:27am | Jul 9, 2007

Yesterday's UK Sunday Times article on the Roadster written by Jay Leno

Thanks, Malcolm, for the great link to Leno's article. I loved the following quote:

"In the real world I have a Porsche Carrera GT, I have a McLaren F1, and anybody that tells you they’ve taken those cars to 200mph is a liar. They haven’t. Believe me. I did a couple of hundred laps at Talladega and the fastest I got to was 190mph – on a track. By myself. And it was scary. Nobody does those speeds on a public road. If you do, you should be in prison. The real-world fun of acceleration is between 40mph and 80mph."

Having only achieved 120 myself -- not on a track but long enough ago for the statute of limitations to have exipred ;) -- I completely agree with Mr. Leno. A real driver has to exceed 100 MPH now and again, I suppose, but the majority of fun, most of the time, comes between 40 and 80. As long as the Roadster (and the Whitestar) perform well in this range, they will put a glint in the eyes of those who drive them. Maybe we'll see a Roadster in Jay's Garage, one of these days. In the meantime, check out the Baker that Jay talks about in the article. It was pretty cool in it's day and some of us still find it so...

There seems to be 3 schools of thought on regenerative braking:
1) Tied in to accelerator controls, so it is activated when letting up on the accelerator.
2) Tied to the brake pedal and coordinated with the hydraulic brakes.
3) A compromise, with light to medium regenerative braking on letting up the accelerator, and heavier regen upon pressing the brake pedal.

There are arguments in favor of all 3 approaches, but somehow I think a compromise is in order. ;)

To clarify a point: The "B" position on the Prius shifter applies engine braking, not regenerative braking, when you let up on the accelerator. It is only to be used on very long downhill runs. Yes, the Prius has 4 independent braking systems - hydraulic, parking, regenerative, and engine braking (spinning the engine without fuel or ignition). The Prius does activate regen from the brake pedal, modulating it smoothly with the hydraulic brakes, but can also activate regen via the cruise control

Denis

5:28am | Jul 10, 2007

I have a question for Greg. Is the ABS/Traction controller deciding when the physical brakes come on while controlling the pressure based on brake pedal position, wheel slip and regen braking rate? Another Question, can you use regen braking only, I mean no brake pads except for parking brake? And would this be safe? The system could possibly dissipate excess captured current through cooled coils as mentioned above by Kert.

As far as regen braking profile I would simply model existing ICE cars braking characteristics profile as the default profile. The normal slowdown when you lift your foot from the accelerator and braking rate for brake pedal position. This would insure a smoother transition for the average driver. This could be made more aggressive than traditional but would still follow profile curve.The driver could leave the default profile and go to user selectable and have a 1 - 5 setting to get a more aggresive use of the entire braking system.The regen would be at its best with a all in one ABS / traction and regen controller using the regen to its full flexibility then only using physical braking when needed. The primary goal is to slow or stop a vehicle. To me Regen should be as efficient as possible while accomplishing the primary purpose. People will argue indefinitely on tuning of the regen braking, I see this now.

Loshwomp

6:18am | Jul 10, 2007

Richard wrote:
Cars should coast when you take your foot off the accelerator pedal. Bringing it to a stop is what the brake pedal is meant to do. Anything else is simply an illogical design of the vehicle’s interface and an inefficient usage of energy.

So how long did you drive the Roadster before you arrived at this conclusion?

Anatoly Moskalev

8:02am | Jul 10, 2007

To Roy:

I did not exactly assumed that Tesla is under speed control. I just indicated that this will be a limit case of extra high regen. Such a mode will be very far from usual ICE based car behavior. But it is certain that car velocity (eMotor RPM) should be a factor in how regen is applied so the simplest system will use accelerator or brake pedal and velocity as input variables to determine torque. More general case would be if both accelerator and brake pedals are involved as inputs together with car velocity and surely gear position. In such a case any dynamics could be simulated. Just it makes very big space of possibilities how regen should be used.
The issue with regen is that it is not very clear how to introduce it into car from typical driver habits point of view. Regen could mimic engine braking and it could mimic friction brakes to some degree. So it is big question how to blend it into car dynamics that driver feel it good. I do not know the answer. Answer actually should come from drivers experience so it is not engineering problem exactly. It is customer choices control problem.
For driver like me best regen behavior would be if it is linked more to brake pedal and only slightly to accelerator pedal because I like car coasting without acceleration. It seems that quite a significant number of people would like it similar way too. But I believe that target customer base for Tesla roadster will most likely prefer it other way that accelerator pedal position translates into speed more closely making most regen applied by accelerator pedal. This explains Tesla Motors choice of regen control. May be they overdo it - market will tell when (and if) they really deliver mass produced car and it will sustain road usage by many people keeping them happy customers.

Doug @ Stanford

8:38am | Jul 10, 2007

Just FYI: It looks like the teslamotorsclub.com forum (not officially affiliated with Tesla Motors) was hacked last night. Let's all home that GreenSpeed can get it up and running again soon.

Tony Belding

8:46am | Jul 10, 2007

I've said this before, but I think it bears repeating. . . Put regen on the accelerator pedal, and put mechanical braking on the brake pedal! Don't mix them up! That way it's simple, it's predictable, you always know exactly what you are telling the car to do. One pedal controls the motor, one goes to the brakes, what could be easier?

I'm against putting both mechanical brakes and regen on the brake pedal and then letting a computer decide which kind of braking to use. That may be okay in soulless people-movers like the Prius, where it's only about getting from point A to point B without having to think or feel anything, but in a sports car it would just be wrong.

By the way, when my wife went to "owner training" at the dealer after getting her new Highlander Hybrid she asked "when should I use 'B' mode" and the instructor literally said "never, because we don't really know what it does exactly."

More from the Prius "B-mode" description sites:
* "The only time the physical brakes are used *by preference* is during a panic stop, when the pedal is suddenly slammed down. The system senses this fast rate of change and immediately brings in the hydraulic brakes for faster and safer stopping with all four wheels."
* "all regeneration quits at less than 6 or 7 mph, when the motors aren't turning fast enough to provide useful power"
* ..."between 19 and maybe 10 miles per hour, you can use 'B' to slow down in an energy-productive way, and essentially drive around in electric-only mode with one pedal -- but be careful to not do something the person behind you doesn't expect without showing brake lights!" (perhaps why our dealer advises customers never to use "B-mode"???)
* ..."having the driveline 'fall on its face' the instant your foot comes off the accelerator pedal may be desirable behavior at times. This may feel familiar to some EV drivers, where regeneration control all comes from releasing the go-pedal in controllers without integrated braking features."
* ..."in the '04 {Prius} and since ... little or no pressure is sent to the wheel brakes until the system has extracted as much regeneration as possible."

Jonas

3:08pm | Jul 10, 2007

All of this talk about the way things should be is irrelevant. Tesla already made their decision for the Roadster. The accelerator pedal controls the motor, and the brake pedal controls the brakes. So under normal driving, one should aim to never use the brake pedal (except under 3 mph, where regen is turned off) if one wishes to maximize range. Given that full regen in gear one is supposed to slow the car the way gear one on a normal car does, this is pretty strong braking, and the normal friction brakes won't be necessary in almost all situations not requiring a full stop.

Richard made a good point that changing the position of the accelerator all the time will result in many regen cycles, so the obvious solution to this is to keep a steady foot and use cruise control whenever possible. Also, let your speed gather a little bit on the downhill and decrease a little on the uphill (this works to save gas in a normal car also, but be sure you don't screw up the flow of traffic by going too fast or too slow).

And just to voice my opinion, although it doesn't matter, I like the decision that Tesla made, and I think that they should make it work the same way in the White Star.

At the Tech Museum in San Jose:http://www.thetech.org/exhibits/green_by_design/
"Regenerative Braking
Learn how electric cars can recapture energy typically lost during braking.
An electric motor is used to slow down the tire, while producing electricity to charge the batteries."
"Supercapacitors
Race two cars that are powered by supercapacitors instead of batteries. Supercapacitors have been called "lifetime batteries" since they can survive a million charges before they need to be thrown away."

In spite of some comments saying that the Tesla regen design is fine, here are some of the issues I see with it:

#1: "Coasting" with your foot off the "go pedal" may not offer enough regen to stop you quick enough without resorting to the friction brake pedal.
#2: Many people will step on the brake pedal out of habit even if the eMotor regen would have been able to slow them down enough anyways.
#3: No regen on the front wheels so you always have to use the friction brakes in front when slowing down using the brake pedal.
(Typical brake bias says that more braking force needs to go to the front wheels)

Most of these concerns revolve around the idea that "foot off the go pedal" may not provide enough negative torque to slow you as much as you need so the friction brakes are used instead of extra regen. People seem to be assuming that the Roadster will provide enough regen but I am concerned that it won't actually invoke as much regen as a brake integrated system would.

Recall what Greg wrote:
## there are some who would prefer the car to coast when you (take your foot off of the throttle pedal)

So that tells me that they are considering having less "foot off the pedal" regen then what might otherwise be optimal if efficiency was the only design goal.

Now others have gone back and pointed out that 1st gear will offer enhanced regen, but recall what Tesla says in their FAQ:http://www.teslamotors.com/learn_more/faqs.php
"If you do not feel like shifting, you can drive entirely in second gear: acceleration even in second gear is remarkably fast."

So the EPs are driving around only in 2nd gear, Tesla says it is OK to always leave the car in 2nd gear, yet we are hearing that there may not be a whole lot of regen going on in 2nd gear. With the Roadster's acceleration you are likely to come up fast on traffic and need to hit that brake pedal often if letting off the of "go pedal" doesn't slow you quickly enough.

If we weren't so touchy about range I wouldn't keep making a big deal about this, but I cringe every time I think about how much those friction brakes may get used.

Jeremy

6:21pm | Jul 10, 2007

Life is great when an automotive company can seek to put out a high quality durable exciting fun envious heart pounding fast more then meets the eye driving machine. You never have to use primordial converted fuel (optional solar array). While most all of us sit in our congested stop and go cities wasting billions of gallons of primordial energy that has been forming for 100's of million years. Just to be sucked out in .000000...1 percent of Earths existance to push our polyphhat polyphhucinn polyaccess around from home to Mk Deaths, Wall Us aparts, Star sucks and back home. Thank gluons for Tesla's endevour, and to wisdom to keep a living journal of all our thoughts to forever share with the universe.

ssim--tesla motors oh yeh...

Joseph

6:41pm | Jul 10, 2007

Jonas wrote

"All of this talk about the way things should be is irrelevant. Tesla already made their decision for the Roadster."

But we're whiny little EV-nerd/customers that want their way!!!

T.J.

8:44pm | Jul 10, 2007

The website "The Energy Blog" has interesting info. on batteries, EV's and thin-sheet solar- Including Mitisubishi and other Japanese co. making cheaper, more powerful Li-ion batteries. Also article on ZAP EV co. working with Lotus on EV with wheel hub motors.

Michael

2:31am | Jul 11, 2007

I agree with TEG in that the real point that is probably most important is the impact that the additional braking regen will have on range of the vehicle. Since we expect the Whitestar to be a larger and less efficient vehicle, the only smart way to go is to consider all possible avenues of energy recapture in order ot extend it's range to make the vehicle worth considering to as many consumers as possible.
Since EVs will be constrained by the capacity of the batteries available, focus needs to remain on reducing aerodynamic drag, reducing energy expenditure, and increasing energy recapture. I agree that the Roadster could be considered special to the sporting crowd and will make certain allowances to improve the driving enjoyment, however I believe it also needs to be recognized that the Whitestar is being targeted to a different audience where extreme sport attributes are not at the top of the list of priorities.

Malcolm Wilson

4:27am | Jul 11, 2007

This is one of the most important discussions in these blogs, since the particular choice / implementation of Regen is a key way to encourage drivers away from ICEs - or scare them off, if engineering designers get it wrong.

Yes, the decision has been made with regards to regen in the Roadster, but the Roadster fulfills a unique position. It has to be "The EV tied to the ICE legacy", but it will allow future vehicles to push the boundaries still further.

Maybe some engineering implementations will become tried and tested favourites - Tony's "Accelerator for Regen/ Brake for Mechanical" is an excellent example.

On the other hand, the limited numbers of gears, the driving on different inclines or just the opportunity to think differently about the pedals in a car may yield something different. Possibly better.

For example, one advantage of ICEs is that the greater number of gears allows for several different levels of engine braking when coasting. To mimic this in an EV you could have regen strength linked to the two or three gears, but also allow for a momentary touch on the brake to increase regen strength if needed. So this could be used to provide two levels of regen for each of the gears.

Depressing the brake pedal engages the mechanical brakes as normal.

Of course, this idea assumes that EV designers will always have to mimic characteristics of the ICE, which is not necessarily ideal.

Maybe there are different and better ways to operate a car. Who knows. The point is that a "Detroit mindset" is not necessarily the best starting point from which to explore new ideas.

After all...."More of the Same" is causing all sorts of problems for the Big Three.

Pete

11:57am | Jul 11, 2007

I think some of the people on this blog are missing the point of the comments raised. Just because Tesla does something a certain way does not mean it is correct. They have yet to deliver a vehicle to a customer and some are posting as if they have the ultimate solution for regen already in place. This will take time to figure out and some of the suggestions raised are just as valid as the counter points made.

In my mind having breaking and regen separate does not make sense as the computer loses control. If it is tied to braking then the computer can maximize regen based on braking with the goal of avoiding use of friction brakes unless the speed of breaking indicates an emergency stop.

1) maximize regen
2) minimize brake use / replacement

Are there any other requirements here? Another nice thing would be if regen could be tied to cruise control so you could lock in a speed and maintain for hills and decents using regen instead of braking on downhill sections.

Tab Simon

2:12pm | Jul 11, 2007

Hi Boy's,
My question is if and when you design another Tesla car would it be possible to add a second set of batteries and an on board charging system? While running off of one bank of batteries, be charging the spare set of batteries and switch over when needed? I know this would jack up the price alot, but could it be done so the car could run alot farther? Also what is the price of replacing the battery bank or the price of each battery?

mark f.

3:34pm | Jul 11, 2007

I have eagerly kept up with the development of the blackstar tesla, and believed all the hype.
Now with the latest VP. passing Safety Testing, the car is coming back down to earth.
I see the performance/ range specs have come down and the curb weight went way up.
My question is-" how come the tesla is so much heavier. I read your article stating that
a little here and a little there adds up. and I'm sure that is true. you didn't do it without good reason.
I still would like to see some more detailed answers.
My peeked concern is because the tesla is way heavier than the Lotus Elise it was designed from.
The US. lotus elise is
1,975 lbs. http://www.puresportscar.com/elisespecs

yet the Tesla is
2700 lbs.

this is done with lotus engineers on staff?
I would really like to know more of the why?
again, I know you have your reasons.

CM

3:50pm | Jul 11, 2007

Ooops, I goofed. The Prius applies both engine braking AND regenerative braking when the shifter is in the "B" position and you let up on the accelerator. Still, I was right about it only to be used on long downhill runs. Think of it as a substitute for tle "L" position on automatic transmissions.

I once shifted my Prius into B by mistake then drove it on the freeway. It sure behaved differently, for a moment I thought I'd left the parking brake on! ! It also reduces the gas milage.

Pete

8:25am | Jul 12, 2007

Tab,

Adding a second battery would not help since the requirement is a batter with capacity to take a charge (to still allow regen). If you went to the expense of adding a second battery or, more likely, just increasing the capacity of the main battery, then you would also want to make use of that battery all the time (not just for regen). So you end up at the same point. As Anatoly points out, given the efficiencies of power usage and regen the only real case where you won't have "space" in the main battery for regen is if you started with a fully charged pack and then went down a large hill. In any case adding a second battery does not really provide any advantage over increasing capacity of the main battery. The system is already in place to charge the battery based on regen and if you did have a larger pack you would want to charge it fully for maximum range rather than leaving it partially discharged with the hope of charging it more through regen.

David Row

8:46am | Jul 12, 2007

I take exception to your comment that "almost everyone" wants regen on the accelerator.

There are only a few people with multi-year experience with factory EV's that have integrated regen. And they are currently driving Toyota RAV4-EV's.

Nobody asked OUR opinion. And the majority opinion does not support Tesla's position.

On the other hand, the RAV is an SUV for city/family use. Not a sports car. Sports cars only have two speeds: accelerate and decelarate. Real world cars need more options.

Just to clarify here: I personally will never buy another EV if it forces itself into regen mode without my telling it to. Not even a Whitestar (or Tesla Roadster if I could afford it).

# mark f. wrote on July 11th, 2007 at 4:34 pm
## My question is-” how come the tesla is so much heavier (than an Elise).
## The US. lotus elise is 1,975 lbs.
## yet the Tesla is 2700 lbs.

For starters, to get a useful range, they have a 900lb+ battery pack (ESS).
With that added weight they need to strengthen and upgrade other components.
Beyond that they felt the Elise was too spartan and uncomfortable so they made a lot of improvements.
For instance, the seats are more comfortable and it is easier to get in and out of the Tesla.

Batteries (energy storage) is really the thing that makes a typical EV be heavier than a fuel powered counterpart.

Tesla uses Li-Ion batteries which end up being lighter than previous technology (Lead-Acid or NiMH), but ongoing battery improvements are still needed to make EVs catch up to fueled vehicles in the weight department.

I think it's funny that so many people want to mimic the driving styles of gas powered cars with regard to coasting. Personally, I drive a stick and use my brakes only when I have to. I say, crank the regen up to the max - there's no question of balance at all. I won't be completely happy until I can stop using my brakes altogether and keep my foot on the accelerator. And if the regen is strong enough that the traction control system has to engage, why bother putting brakes on it at all? You are already operating at the edge of the envelope. If people need to feel like they are doing something, give them a toggle petal they can rock back with their heel.

But I do have a question concerning safety. Is there a threshold by which regen causes the brake lights to come on? My downshifting doesn't cause me to slow that quickly, but I constantly check my mirror to make sure I'm not going to get rear ended in traffic. I'm sure with very aggressive regen, you will want your brake lights to come on to alert the drivers behind you.

Of course, you don't want it to be too sensitive or you're going to get the Christmas tree lights you see blinking up and down the highways today. Keep the threshold high enough, and maybe in our electric car future, brake lights in front of you might mean something again. This is the only balance I see that's needed. Provide everyone else with an optional upgrade so they can have their dials and levers to remind them of their ICE coasting days! :-)

Leave the dials and levers off my car. You can keep the brakes while you are at it as well.

Billy

12:53pm | Jul 12, 2007

Another thought I had to support tossing the breaks altogether is the fact that this car can run backwards simply by reversing its motor. If you had to make an emergency stop, couldn't you provide ACTIVE breaking resistance from the motor, beyond the resistance you get from regen breaking? If this motor can push the car to 60 mph in 4 seconds, it should be able to stop it in less time, since you now have all of the resistant forces working in your favor instead of against you. Keep in mind, this would only be needed for emergency stopping, so impact on range wouldn't be a concern here. Regen braking should provide you with more than enough resistance to stop you in your day to day driving (assuming we take it down to 0 mph). Rather than spending research money on developing brakes that have less parasitic resistance when not in use, I'd say get rid of them all together and save the weight and money.

Of course, since you'd only have breaking resistance on your rear wheels with this setup, you might have to compromise and supplement this with disc breaks on the front of the car, and control them electronically (without a break pedal). Then you could use a torque petal that seesaws so you press with your toes to accelerate, and your heel to stop. And since the disc brakes on front would be computer controlled, you could take it a step further and use the heel direction on your accelerator for your reverse. Then when you want to stop while backing up, you just push your toes forward again. :-) Now I can go forward or backwards without taking my hands off the wheel, or my foot off the accelerator. And the break lights and reverse lights are activated automatically.

Drive by wire is coming, and that will include the breaks and steering. The aviation industry has done it successfully for years.

# CM wrote on July 11th, 2007 at 4:50 pm
## Ooops, I goofed.
## The Prius applies both engine braking AND regenerative braking when the shifter is in the “B” position
## and you let up on the accelerator.

From http://en.wikibooks.org/wiki/Toyota_Prius_driving_tricks
""(The 'B' Shift position) tells the Prius to attempt to *EMULATE* "engine braking" in a conventional vehicle. Depending on the vehicle's speed and the battery SOC (state of charge), the Prius will do this USING REGENERATIVE BRAKING and/or high-RPM zero-fuel-flow engine braking.
Engine braking is inefficient because it uses the engine as an air pump, converting kinetic energy into heat. Unnecessary regenerative braking is also inefficient because of energy conversion losses. (Regenerative braking is good when it replaces friction braking, but it's not as efficient as coasting at a constant speed.) Because of this, "B" mode is not recommended for general driving.""

So, depending on battery SOC, vehicle speed and other factors, B could be used to get some enhanced regen, but chances are most people would accidentally invoke extra ICE braking sometimes so it is probably best left to the efficiency experts, or (as has been said) left to long downhill grades for the average person.
My RangerEV has a similar transmission arrangement with the conventional auto "D" settings, and then the "E" setting which feels a lot like "B" in the Toyota Hybrids. But in the case of the RangerEV, there is no ICE for engine braking so the effect is entirely enhanced eMotor regen. With the RangerEV is is perfectly fine to leave it in "E" mode all the time except if you need to merge onto the freeway or achieve a higher top speed.

This brings me back to a point about the Roadster... Tesla offers one transmission variant. Most other "conventional" sports cars offer you the manual transmission or auto transmission option. Tesla is trying to provide their Roadster to people used to either choice. So for those used to a manual transmission you can shift into 1st when you think it is prudent (to get more low speed acceleration and/or more regen effect), but for those used to an auto transmission you can just leave it in 2nd all the time.
Further, people used to an automatic transmission may not expect much engine braking when letting off of the "accelerator" pedal, so they are more inclined to hit the brakes as soon as they stop needing to accelerate. I would bet those coming from a manual transmission ICE sports car will be more inclined to use 1st gear, and more inclined to make use of an "simulated engine braking" (regen), whereas those coming from auto transmissions are more inclined to use the friction brake pedal a lot. Part of this whole debate going on here is over the differences in expected driving dynamics for people coming from two different modes of operation. If Tesla was just making the vehicle for those used to manual transmissions then the "enhanced" regen would likely be fine (from an efficiency standpoint), but the problem is for those drivers coming from auto transmission cars.

David Dodson

3:12pm | Jul 12, 2007

I was wondering if you charged the batteries directly with the regenerative braking. It seems, since batteries are slow and innefficient at charging it would make more sense to use a capacitor as an intermediate step. They can be charged much more quickly and then use the capacitor to recharge the battery bank.

Of course, capacitance requires a great deal more mass for the equivalent power retention so there would be a fine tuning involved.

I recommend you do the 'slideshow'... the Roadster stuff starts 4 slides in.

Love that interior!!

Billy

8:20pm | Jul 12, 2007

I agree completely with TEG2's comments above when he says,

"the problem is for those drivers coming from auto transmission cars."

As a stick driver, I tend to be overly critical of people overusing their breaks on the highway and in traffic (hence my Christmas tree light comment earlier). But the truth of the matter is that most people drive automatic cars, and the only real way to slow down in an automatic is to use your breaks. And since most drivers are used to pressing their breaks every 15 or 20 seconds (this MAY be a slight exaggeration for some), it's easy to understand why your average person would want to keep pressing their breaks every time they want to slow down, or just coast along a slight decline with your foot flat on the floor and let your engine have some idle time. But manual drivers don't drive like this (especially if they have a large displacement engine that will quickly slow their car). You won't see a manual driver coasting down hill with his foot on the clutch. He'll let the hill keep his engine turning, he'll just use less pressure on the gas pedal.

I'm always cursing people in front of me for braking so much, but then I go on a business trip and rent an automatic car and find myself forced to engage in the same stop and go mode as everyone else. I'm also prone to stomping on the break as I try to down shift thinking it's the clutch - man I hate those automatics. But I think eventually people will learn to love leaving their foot on the gas (or maybe I'm being too optimistic here - though that might be a first).

chrisincanada

9:00pm | Jul 12, 2007

It would be great if you could make an high quality internet Tesla commercial. Something that can be posted on various websites like Youtube. It would generate a lot of discussion, debate an interest, not just on the Tesla roadster, but for EV's in general. It could be half about the car and 1/4 about Tesla Motors company and 1/4 about the benefits of switching to EVs and getting off foreign oil while reducing greenhouse emissions at the same time

Could start off with that deep voice thats always in movie trailers...

"Imagine America with out the need for foreign oil" (Show video of troops in the middle east packing up and going home" while playing some uplifting song

"You no longer need to imagine, introducing the revolutionary, next generation of vehicles."

Fade to black.. then pops on the screen briefly then fades out followed by that fades out leading to another feature like , with each feature, it fades quicker than the feature before it, picking up speed, until the last feature, the most important, there is a big base hitting BOOM, lots of smoke maybe, as the smoke clears you see the Tesla Roadster all shiny and spinning, with the words 100% all electric vehicle over top. The video then pans over the interior and engine, wheels etc. Have some good uplifting music playing etc. It fades to black, music finishes, the words "Its here" comes on for a few seconds, than fades.. commercial ends.

That would be just the kinda commercial we need so that myself and the army of Tesla motor fans out there can spread it across the entire web and world.

Feel free to use any of that =)

chrisincanada

7:27am | Jul 13, 2007

Fade to black.. then pops on the screen briefly then fades out followed by that fades out leading to another feature like , with each feature, it fades quicker than the feature before it, picking up speed, until the last feature, the most important, there is a big base hitting BOOM, lots of smoke maybe, as the smoke clears you see the Tesla Roadster all shiny and spinning, with the words 100% all electric vehicle over top. The video then pans over the interior and engine, wheels etc. Have some good uplifting music playing etc. It fades to black, music finishes, the words “Its here” comes on for a few seconds, than fades.. commercial ends.

Sorry I must have had a bad case of dyslexia or something, it should read like this so please fix it

The "weekly" blog updates appear to have become "bi-weekly" updates (if we're lucky). I thought the 4 blog categories were supposed to INCREASE the amount of information being given out!

Iz

11:13am | Jul 13, 2007

# Doug @ Stanford wrote on July 10th, 2007 at 9:38 am
# Just FYI: It looks like the teslamotorsclub.com forum (not officially affiliated with Tesla Motors) was hacked last night.

Doug, is there additional information regarding site recovery? The site has been down all week. Forum appears to have been taken over by spammers.

Pete

2:09pm | Jul 13, 2007

If you search for "electric car" on google the chevy volt site and zap comes up before tesla! You really need to pay attention to SEO (search engine optimization) and at least change the tile of your default document to something with some keywords.

With a focus on getting a quality site to drive word of mouth you are really missing out on exposure by not optimizing the page titles, link and description text in your site.

James Anderson Merritt

4:24pm | Jul 13, 2007

I keep hoping to see a Tesla on the street in Santa Cruz. I've seen a ZENN in traffic next to me on Ocean Street, and also an AC Propulsion eBox (leaving me in the dust) on Hwy 280 "over the hill," but no Roadster in motion yet. Twice I've spied an Elise from a distance on Hwy 17, momentarily hoping it was a Roadster, only to be disappointed when it caught up with me (or vice versa).

Incidentally, for the Tesla PR crew: there is supposed to be a Mathilda Place (downtown Sunnyvale Office complex) "Spare the Air Transportation Fair" on July 19th. Among the "invited exhibitors" listed on the notice I received today are "electric cars." I hope the Roadster will be one of them! If not, there are more than a few people working in this building who could afford a Roadster (at least one has an Elise!), and there might be TV coverage, too.

Anatoly Moskalev

4:42pm | Jul 13, 2007

To Dale:

I always thought that blog split into 4 streams was done to discourage people to participate too actively and to release Tesla Motors from implicit obligation to publish every week into publishing only if Tesla Motors need it. I think problem for Tesla Motors with this blog is that it is way too active for a business entity. It goes engaged like a media of some sort. Been a business Tesla Motors just could not have enough interesting information to keep news hungry crowd here happy most of the time. To me it looks like sort of a trap with Intenet marketing idea of Tesla Motors. I enjoyed the implicit nature how they manage previous issue with pressure to talk regularly by blog split and it worked for a while. But now same pressure come back again.

If you would like to help Tesla Motors let them go free from any pressure to publish. Would they need to say something they would do publish but otherwise they probably would like just to let bloggers talk to each other for a month or two. From my technology development experience I could guess that Tesla Motors team should now be under extreme stress to deliver the product to public. And as extremely very common in this position product does not work as they expect and they keep fixing, tweaking, testing, fixing, tweaking, testing ... ad infinitum. It is too hard to keep up kind of a media activity level blog under these conditions I guess.

Doug @ Stanford

6:32pm | Jul 13, 2007

#Iz wrote on July 13th, 2007 at 12:13 pm
## Doug @ Stanford wrote on July 10th, 2007 at 9:38 am
## Just FYI: It looks like the teslamotorsclub.com forum (not officially affiliated with Tesla Motors) was
##hacked last night.
#Doug, is there additional information regarding site recovery? The site has been down all week.
#Forum appears to have been taken over by spammers.

Iz, you probably know as much as I do. I know that Greenspeed was out of the country and not really in a position to take care of site maintenance. So it will probably have to wait till he gets back to get fixed. Hopefully that will be soon. Last Monday night, I noticed only a couple lines of text on the main page. They announced that the site had been hacked by some group... don't remember the name, though. Since then a single "General Discussion" forum full of spam has been set up. This must be a real nightmare for Green and I for one really miss the site.

David Row: Thanks for your opinion on regen implementation. It is important for the rest of us to hear from ev drivers. I do not feel qualified as I have no electric car experience, but I did think that people would easily adapt to either system. You have a strong objection to regen via accelerator pedal. Can you tell us why? There is a scenario I imagined: To relax my foot on a long drive I like to be able to take my foot off the pedal. If the car has cruise control (which the Tesla Roadster does) then this can be used to solve the problem. If the car did not have cruise control, or it was inconvenient to use (like in heavy traffic), then I would prefer to have the car coast while I removed my foot for a brief exercise.

Billy: Your comment on not requiring brakes is valid as the system you describe is used by PML Flightlink on their Mini project http://www.pmlflightlink.com/archive/news_mini.html This car has 4 wheel drive and no mechanical brakes. I however, do not agree with this arrangement because there should always be a mechanical brake back up system incase of power or control failure. Secondly if you stop on a slope at a red light you would consume energy in the Mini just to stay still.

David Dodson, Pete and others: Ultra capacitors are VERY expensive and in Tesla's case would make regen much more complicated. Price is the main reason Tesla does not use ultra caps. If the price comes down enough, Tesla has already said they will use them.

Pete: Regen is tied into cruise control.

Some people seem to forget that the Tesla Roadster is a rear wheel drive car and most braking effort is done by the front wheels. The regen braking is most effective at high speeds and minimal at low speeds. Too much regen braking at high speed would cause the rear wheels to slip and send the car into a skid, even though the actual stopping rate would be much better with the front wheel brakes applied. This is why Tesla has a limited slip algorithm in the regen software. This feature does not imply that all the stopping energy in a high braking mode can be recovered. If Tesla wants to recover significantly more braking energy in the WhiteStar it will have to be front wheel drive or 4 wheel drive.

Bob Guevara

9:11pm | Jul 13, 2007

Now this really doesn't pertain to regenerative braking but I didn't know where else to write.
Also maybe this isn't such a new idea, but it occured to me that one of the drawbacks of an electric car is the time it takes to recharge it.
Would it be possible to have something along the lines of a battery system that was removable and replaceable in each vehicle so that when the charge is getting low you would pull into a business where the discharged battery pack could be removed and replaced with a fully charged pack.
These businesses (something like gas stations are now) would take the old battery pack and recharge them and have them available for the next customer.
Also if these businesses were equipped with alternative methods of generating electricity such as solar panels or possible wind powered generators you would further reduce the use of oil or coal to create electricity.
Hopefully I'm not way off base.

scott messick

11:27pm | Jul 13, 2007

Regarding the regenerative braking discussion. We have considered the proposition of purchasing a Telsa once all these quirks get worked out.

I and and my spouse each drive Rav4EV vehicles. We both agree, as do many of our fellow EV friends, that having control of regen as well as the ability to coast is vital to the effective range. Yes it takes some getting used to; a learning curve if you will, but is essential in real-world application. In fact, we thought having greater control than the Rav4EV allows us would be useful.

We envision a lever in front of the steering wheel much like the multi-level "jake-brakes" used in Europe.

Scott Messick[Contact details deleted]

PS. In the world of media we are constantly amazed at how smart and adaptive the consumer is.

Iz

10:13pm | Jul 14, 2007

Doug. Thanks for the update. It will be tragic if a site backup was not available. I miss the site also. It kind of expands on topics these blog entries and postings initiate.

The group that hacked the site left this:

"Hacked by DeLi_CaN .:. VatanAy 1923Turk Grup .:. Efeler".

Would be nice if they applied their talents to more constructive endeavors.

terry

10:07am | Jul 15, 2007

For braking, why not use conventional braking techniques; however, only implement them in a emergency need situation and during times where the batteries are fully charged. Have the system computer switch between conventional braking (CB) techniques and regen braking, depending on the situation:
IF
Batteries full OR emergency braking needed OR ABS type situation THEN
braking technique = Conventional braking
Else: braking technique = regen.

end if
Good luck.

Brent

6:53pm | Jul 15, 2007

#Bob Guevara asks about battery swapping:

The idea of quick-change batteries has been discussed thoroughly in previous blog conversations. As you might imagine, a number of considerations would go into actually making such a system. I don't believe that the Roadster, in its current configuration, will ever use swappable batteries. The battery is now actually inserted from below, and requires that the car be on jacks. I hear it takes as much time to replace it as it does to recharge.

Of course, it may be that future cars are designed differently. But it's not clear, even then, that swappable batteries will work out, not at least until they become substantially cheaper, smaller, lighter, and longer-lasting. Here are some of the points that have come out of previous discussions:

1) Economics: who's going to buy the swapping batteries? They now cost on the order of $20,000 each. It's not likely that TM is going to make a bunch of spares for the few drivers who travel more than 200 miles in a day. Nor would gas stations, which run on the thinnest of margins, likely be able to afford such an inventory. That said, Th!ink, in Norway, is contemplating a battery rental system (using TM's battery packs), so there may be a way to make the economics work on that basis.

2) Safety & Engineering: the Roadster's battery weighs around 1,000 pounds. Such weight ought to be firmly attached to the car. Some people have argued for a modular, "box" system, in which the battery is divided into smaller modules that can be pulled and plugged at will. No matter the system, however, I have the sense that safety concerns may well get in the way of the quick swapping goal. I would think that it would take at least as much time to change a battery as it would a tire (20+ minutes for us non-race-car drivers), and probably a lot more. You can put a good amount of charge into a battery in that time.

3) Battery quality: current batteries wear out relatively quickly. TM will guarantee its battery for 5 years, and it expects it to last at full rated capacity for about 6 years. Still,a battery one year old isn't as capable as a new one. A swapping system might create an odd calculus among drivers hoping to get rid of their older, worse-for-the-wear batteries. I suppose someone could come up with a battery grade calculation, but it will have its difficulties. Imagine finding yourself in some backwater and faced with changing that beautiful new battery for an old beater.

4) Future technology: in the time it might take to build out a network of swappable batteries, we may see the 500-mile battery. For many (most?) of us, 500 miles is as much driving as we'd care to do in a day, after which the battery can just be charged overnight. At that point, I think the idea of swappable batteries will become redundant.

Pete

11:07am | Jul 16, 2007

>I however, do not agree with this arrangement because
>there should always be a mechanical brake back up
> system incase of power or control failure.

The braking system is fully dual circuit and each wheel is independently connected to the brake system. Each wheel has several levels of redundancy so any single failure will never prevent the vehicle from operating safely.

Someone said, "Ah but there is only one battery and if this fails or if a main fuse blows the vehicle cannot stop!” In fact when the vehicle is moving, the battery is no longer needed for braking power since the wheels themselves generate all the power needed to stop. This is the basis of regenerative braking and PML system can regenerate down to stop."

You can also have a mechanical failure and there is some signal to trigger braking in any case. I think regardless of implementation safety is a concern and something that needs to be solved but to say that regen braking is not safe is just premature at this point.

AlexBG

12:14pm | Jul 16, 2007

Why don't you do it just like in Prius? I have one, and it's pretty well tuned. When you release the throttle pedal it regenerates slightly, just to mimic the ICE-style of engine-breaking but when you press the brake pedal it regenerates as much as it can, adding the force from the brakes, if the electricity produced is over the limit that can be stored in the batteries. And, when you go down the hill, you have a special "gear"(B), which acts in the same way, but far more aggressively stopping the vehicle, this time combined with the engine-braking effect, when needed.

My opinion is that it is a necessity for the driver to have some control over this. In the form of options/profiles *together* with adaptive algorithm. (BTW, the Prius adapts too, distinguishing between highway and city-type of driving, and all between). In an electric vehicle, where every system is electrically controlled by software, it would be odd not to have options regarding the vehicle's dynamic behavior. In theory, if your electrical systems are cleverly designed, you can greatly enhance the functionality of the vehicle even after it's release by just updating the software. My old SegWay behaved totally differently after it's software upgrade from the manufacturer. It not only had new sounds and functionality, but moved and felt better. It even became twice more silent! Just by *software*!

I would also recommend you not to waste your energy to re-invent things others have done and use similar features from other like products. Just drive a Prius over this frozen lake in Sweden and you'll see what I mean. (I bet you've already done it, but others may have not :-) The feeling of a total static control on unstable surface cannot be compared to any 4x4 vehicle with a classical engine only. You can not only climb a curb with a great control and precision but you can actually chose the height on which to stop your car, "hanging" over the curb! You can swing it up and down the curb, just playing with the pedal! :-) I hope that Tesla Roadster would have similar characteristics (not only dynamically but also semi-statically), even though only few of them would be driven in such extreme conditions, like on ice and in snow.

As for those who have just discovered the fact that any electrical motor is not only a dynamo in reverse but also a powerful, electrically controlled brake mechanism, I would like to remind that this effect is used from years in trams and underground railways, who send the recycled energy back to the electrical grid and use their brakes only in the last few meters every time they stop. To have idea how much energy is, well, if not saved, then at least not turned to heat just like that, I will state this curious fact: on the last scheduled inspection of my Prius (75 000 km/46 000 miles) it turned out that the front brake pads are worn out by less than half and the rear ones are almost as new. Compare this with a sports car that "eats" it's pads every 10-15000 miles and you will understand why doing-it-the-electric-way is so important, for the nature and for you.

Andrew Kelsey

8:12am | Jul 17, 2007

The PML Flightlink MINI and the Lightning, both of which use 4 in-wheel motors can't be considered serious competitors for the Tesla....not yet anyway! I read that the Lightning is going to cost £150,000 ....yes pounds....that's $300,000 in round figures or three Teslas. I know which I'd prefer! The Mini would have to be a similar amount I would think but they probably won't build it. To be honest I can't see either project winning many customers especially if they're using the expensive Altair-nano batteries. It would make more sense for them to do a deal with Aston Martin and produce an electric version of a car that people already pay megabucks for and might be persuaded to buy in an electric form. That said the in-wheel motors could make sense in a future Tesla car combined with the Tesla ESS. You could do away with the transmission, which has been a headache for Tesla I believe, and the brakes. 640bhp should make for interesting performance! Apparently unsprung weight is not the major problem it has previously been thought to be. I'm not totally convinced but it looks like it might be a route worth considering.

Brandon

10:22am | Jul 17, 2007

DoD is offering $1 Million for an 8.8 lb battery pack capable of producing 20 watts for 96 hours. If I did my math correctly, thats an energy density of 1.73 MJ/kg. According to Wikipedia, Li-ion batteries max out at about 0.72 MJ/kg (A pack of A123 batteries producing this much energy would weigh ~39 lbs). Even the EEstor claim would only amounts to 1.0 MJ/kg weighing in at ~15 lbs. It will be interesting to see if anyone can achieve this goal. Whatever is conceived I assume could cross over to the EV market, providing lighter and more powerful energy storage systems.

Ryan Lamansky / Kardax

11:04am | Jul 17, 2007

This is slightly off-topic, but has Tesla switched to a one-blog-a-month thing? I'm not complaining; I'm mostly curious if the recent delays between blogs are intentional :)

----

Editor's Answer: Intentional, yes. Desirable, perhaps not. We are all a little busy ;-) There is a new blog article on the way ... soon.

Dave D

1:35pm | Jul 17, 2007

Hey Guys,
First, thanks for all the great work and for these blogs. It's a wonderful way for us to learn more about what is going on and why you made many of the decisions/tradeoffs that you did.
I have to agree with Andrew and where he's going with the questions about in-wheel motors. Clearly you guys have done lots of homework and testing in this area but maybe there is something to it if Toyota can win a 24 hour race by utilizing in-wheel motors along with regenerative breaks to take a car that finished 17th last year and to make it into a big, 19 lap winner in the same race this year.http://digg.com/motorsport/Toyota_Supra_Hybrid_wins_Tokachi_24_hour_endu...

Don't get me wrong, I'd much rather have a Tesla Roadster than anything else I can see on the market...awesome car guys. But I hope you guys haven't closed the door on considering this if it turns out there is potential there.

"Editor’s Answer: Intentional, yes. Desirable, perhaps not. We are all a little busy ;-) There is a new blog article on the way … soon. "

Arhg! Must... have.. BLOG! Going.. through.. withdrawal...

Get the pizza delivery guy to write one.

Ryan Lamansky / Kardax

7:37pm | Jul 17, 2007

A blog on the Tesla Roadster's upcoming appearance in the Project Gotham Racing 4 game for XBox 360 would be cool. Wallpaper-sized screenshots of a Roadster speeding down the Nürburgring would seriously make my year ;)

What does this have to do with regenerative braking? The Nürburgring Nordschleife has between 70 and 170 turns (depending on one's definition of a turn), which means lots of slowing down and thus regen opportunity. See, I'm on-topic :)

nubo

9:40pm | Jul 17, 2007

Man, you guys are really overthinking this.

A) - pressing the brakes slows the car. Whether the internal mechanism is regen, friction brakes or some combination is something the user should neither notice nor need think about. The car's systems should determine the amount of braking from the force on the pedal. Whatever portion of the desired braking can be done by regen, should be done by regen. The remainder, if any, should be via friction brakes. The computer should be able to fully integrate the two. All done within the envelope of the traction control system, of course.

B) - many drivers of manual trans are accustomed to engine braking. Sometimes it's convenient, sometimes it can even improve stability. It should be available at the option of the driver, in varying degrees to suit their preference. All within reasonable limits, of course.

Doesn't that cover it?

mark

4:41am | Jul 18, 2007

Have a little patience guys, Tesla is preparing to birth a baby. It's probably all hands on deck crunch time dealing with all the last minute details.

Keep in mind that they have to open new store fronts in a number of cities, jump through all the remaining hoops to get the final car into production including legal issues, road blocks initiated by competitors(no I haven't heard of any, but it wouldn't surprise me), any last minute bugs that need to be worked out, etc.. etc..

I could see a GM or Ford busy out production for a critical part with a supplier or commit to buying a years production run of some component just to cause headaches and delay Tesla from hitting production. It is amazing how many legal ways there are to sink a small company.

Right now is the time when I think we all need to cross our fingers and hope Tesla has legal commitments from its suppliers, last minute road blocks don't appear, and smooth waters for production.

Earl

6:43am | Jul 18, 2007

I guess the important question here is really: What kind of regen do the electric fluffy pink bunny slipper cars use :-)

Dale

6:59am | Jul 18, 2007

Three weeks since the last blog entry...
Three months late on starting construction on the WhiteStar factory...
The luster of Tesla is beginning to dull...

Dave

8:14am | Jul 18, 2007

GM keeps saying that the holdup for the Chevy Volt is the batteries.

I was just wondering couldn't GM come out with the Chevy Volt tomorrow if they used NiMh batteries ?
They were used 10 years ago for the EV-1 and the Toyota RAV-4 and they had a range greater than the 40 miles for all electric mode that they are advertising for the volt .

Us "armchair engineers" keep pondering what are the ideal ways to build an EV. (The Roadster comes close). We want to think about it because we want to see if there is any possible way to improve the vehicle such as providing more range, or better driving experience. Sure Tesla has done their homework and has an outstanding design, but there still could be room for improvement. But forget about all that... many of us are just curious and like to learn about this technology by discussing "what if" scenarios.

## The car’s systems should determine the amount of braking from the force on the pedal.
## Whatever portion of the desired braking can be done by regen, should be done by regen.

That is the point that keeps me coming back here. Apparently the Roadster doesn't tie the regen function to the brake pedal as you describe.
As far as I can tell this decision was probably done to avoid having to mess with the already proven brake system they got from Lotus.
I bet with more time and $ they would have considered making enhanced regen the first part of the brake pedal action, but it doesn't appear they have done it yet.

## The remainder, if any, should be via friction brakes.

Yes.

## The computer should be able to fully integrate the two. All done within the envelope of the traction control system, of course.

As far as I can tell they aren't doing that yet. The regen appears to be based on the gear selector and "torque pedal" position.
As far as I know, pushing the brake pedal starts to engage the friction brakes immediately.

## B) - many drivers of manual trans are accustomed to engine braking.

Yes.

## Sometimes it’s convenient, sometimes it can even improve stability.
## It should be available at the option of the driver, in varying degrees to suit their preference. All within reasonable limits, of course.

Well, the regen adjustment controls have been suggested, and I am sure considered, but it appears the only "driver input" available is the gear selector (1 or 2) and the accelerator/"torque" pedal.
Some other EVs do have a driver adjustable regen level, but the Roadster appears to be avoiding that level of driver input.

## Doesn’t that cover it?

Well, yes, I agree what you say seems like the most complete approach, but Tesla appears to have chosen otherwise to keep the brake system more independent, and not allow so much driver control.
I am sure they have their reasons...

Joseph

12:37pm | Jul 18, 2007

"They were used 10 years ago for the EV-1 and the Toyota RAV-4 and they had a range greater than the 40 miles for all electric mode that they are advertising for the volt ."

The reason the Volt only goes 40 miles on electricity (the actual productionversion may be different) is because it is just enough to get through an ordinary day of driving. So that way the battery pack is as small, and cheap, as possible which still achieving a range that will cover most people's driving.

Although since the pack is so small, it will have to survive rigirious requirements.

"Three weeks since the last blog entry…
Three months late on starting construction on the WhiteStar factory…
The luster of Tesla is beginning to dull… "

Tesla Motors has said, in response to a comment on a blog post I believe, that the reason they have not started builidng the WhiteStar factory is because they realised that there's no point in building the factory if the cars aren't going to be sold for a few years. And the "three weeks since the last blog entry," give 'em a break.

# Dave wrote on July 18th, 2007 at 9:14 am
## GM keeps saying that the holdup for the Chevy Volt is the batteries.
## I was just wondering couldn’t GM come out with the Chevy Volt tomorrow if they used NiMh batteries ?

Hello Greg,
This seems like the perfect place to ask my questions. I am an avid Electric car fan, and a Tesla is in my future. My first question has to do with your use of the braking system to regenerate power. I completely understand how it works. What I don't understand is why you don't put a rotary fan system hidden in the front of the car, or a couple of them, that would use the wind through the grill of the vehicle to generate power off a shaft, back to the battery system, thus eliminating the PLUG completely. Wallah! Instant recharge while you drive. My first thoughts was a long squirell cage devise mounted on top in a cavity, or under the front of the car. My thoughts lately were openings in the grill or side panels of the car, directing the wind down toward the back of the vehicle, where it would pass over the blades of the fans and then is ejected out the back of the vehicle. Since there is always wind at and around the vehicle at all times, it would be a very clean way to re=generate the batteries for long trips, and could even be sold back to the grid in your home or power grid such as PGE. I have done a lot of searching for such devises, and they exist under patents on google, and this devise has already been patented in 1989, specifically for this application. I know this is a little long "winded", but please email me and let me know where my thinking has gone wrong, and why you go to such extremes to build such a great vehicle, but in my mind missed the cream on the cake, by not providing for wind energy to re-generate the battery pack.

It's me again, with some more wind energy comments. My second plan, would be to split the battery pack into two. Drive on the one pack, until the batteries dropped to a certain level, while the second pack was charging with the wind generator device. When the computer sensed that the first battary pack was now too low, the computer would begin the process of transferring the second battery set on and begin the charging process on the other pack, thus always having at least half of your life left an any given time, thus you could literally drive around the world without stopping, either for a plug, in the case of your design or gas in the hybrid design. With this method, you could eliminate the expensive break regenerating system your are currently using. The engineering downside, is just figuring out a way to build a caged wind driven fan that is quiet, as Tesla fans (is fans a Fishy word?) are already spoiled, and would not want to disturb the conversations on the street, as they tool along, listening in total bliss. Have I missed somthing, or have your engineers?

Turbines function by converting aerodynamic drag into electricity… the more drag, the more electricity you get. But drag slows the car down. If you wanted to capture enough energy to provide 100% of the motors needs, you’d have to provide 100% drag, and taking 100% of the forward motion, stopping the car dead in its tracks. It doesn’t work :)

And no, you can’t just take 50% and provide half its needs to give it double range. If you cause 50% drag, you take 50% of the car’s forward motion away, causing the motor to work twice as hard, giving the exact same range you started with.

You could accurately say that our universe is designed to make unlimited sources of power impossible :)

Robert

10:35am | Jul 19, 2007

Whats going on lately with the crash testing?? Is the 2nd version almost approved?

Malcolm Wilson

11:44pm | Jul 19, 2007

Off Topic:

Outline of the drivetrain Zytek have created for the smart ev available here:-

OK, I have heard that line before, about the fact that if you have a fan in the front of the car generating wind electricity back to the batteries, and lets say, half the time your going down hill and half the time you are going uphill. Lets face it, when you go up hill, you will create drag, but lets say we shut off the fan when you go up, and turn on the fan when the inertia of the car is going down hill, thus using the forward increasing motion to generate electricity back into the batteries. Take a bicycle, for instance. If you started at the top of Mount Diablo, and coasted to the bottom, you could generate a light that lit the whole time you coasted to the bottom, thus instead of lighting the path down the hill, you stored that energy into your battery pack. Going up hill? Your right, so we shut it off to eliminate drag, and conserve energy, so what happens is the car is either going down, generating power back into the batteries, or going up, shutting down drag, and using power you generated in the down slopes, thus creating more efficency than just using the plug all the time. You might be able to substantially reduce the amount of juice you would need to recharge at night by 25-50%. I know that you think I am a bit whacco, but, I can guarantee I can light the night, very brightly, with the added down hill momentum, a one or two ton vehicle charging down hill, and if you opened all the wind vents going down hill, I could possibly have the whole battery pack recharged by the time I get to the bottom of some of those steep hills. When I go to Tahoe, the trip up would use juice from the batteries, and on the way back, would recharge most of the juice lost going up the hill to the skii resort. Lets face it, going down those steep hills wear out our breaks, right? Let that forward motion slow the vehicle naturally by opening the drag vents, and recycle that wind into usable chargable juice on the way down. Just think about it.

rw

Anatoly Moskalev

10:15am | Jul 22, 2007

To Malcolm Wilson:

The Zytek eMotor and inverter system has 55 kW per 60 kg weight.

In comparison Tesla roadster eMotor and inverter system has 185 kW per about 35 kg weight.

So Tesla Motors system has 3.4 times more power from almost 2 times smaller weight. Power per unit of mass for Tesla Motors system is ~5.8 times better.

I see nothing really impressive with Zytek system you mentioned.

Ryan Lamansky / Kardax

9:50am | Jul 23, 2007

Ronald Wose: Tesla's regenerative braking can recover energy down hills. It exerts negative torque on the wheels, and stores the energy generated in the batteries.

It's still not a source of unlimited power--you're simply recovering energy used to climb the hill in the first place.

CM

12:29pm | Jul 23, 2007

Ronald Wose: The regnerative braking that is already built into Tesla cars is much more efficient at recovering energy than a fan or windmill could possibly be. So no need for that when a better cheaper lighter solution is already available!

Now, for recovering energy from wind flowing over a hill, windmills are the best solution. Tesla Motors isn't in the windmill business, they are quite busy enough developing cars...

Malcolm Wilson

2:22pm | Jul 23, 2007

Anatoly Moskalev wrote
I see nothing really impressive with Zytek system you mentioned.

I agree. And existing manufacturers like Zytek believe that they are pushing the engineering boundaries with this sort of thing. Depressing.

I feel that there needs to be a Tesla Motor Group along with the Tesla Energy Group, licensing Tesla's proprietory AC Induction motor to other manufacturers.

Why hasn't anyone tried to tap WIND power to regenerate batteries yet? Everything been about regen. That's why hybrids get better city mileage than highway. There must be some way to tap the 50, 60 or 70 mph wind passing over the car, and funnel it through without adversely affecting drag or styling, and tap this energy. From the time you're a kid hanging your arm out the window you learn to power of the wind passing by the car. Why not start tapping it. It could be the ultimate in regen.

Alastair Carnegie

11:47am | Jul 25, 2007

China is holding the International Forum on the Innovation and Development of Alternative Fuel Vehicles ( Beijing 25 October 2007 - 27 October 2007)

The aim of this event is to promote advanced, energy efficient and environmentally friendly technologies in automobiles.

China has recently announced its policy to build an innovative country and to achieve the goal of conserving energy and cutting down pollution, this forum is a very significant event for the year 2007 in China.

Looks like it will be an interesting conference, It would be insane not to attend in my view.

"A wind turbine on the car will always increase the aerodynamic drag, and the energy it produces will never be as much as the additional energy needed by the drive motor to overcome the wind turbine’s drag."

Brent

10:58pm | Jul 25, 2007

#Galactic Canibal wrote on July 24th, 2007 at 11:17 pm

#Did Tesla Motors ever road test their multi -cell battery to end of useful life?
#How many packs did they test?
#Was their road testing representative of your average 15,000 mpy driver?
#What were the road condions? , and the weather conditions during test?

From what I hear, there are two cars being driven at an English test track, under very strenuous road conditions and in all weather types, as close to 24x7 as the battery packs will allow.

#How many miles driven before battery failed to deliver max performance as advertized?

Not sure it matters. You're guaranteed 100,000, with a replacement for failed ones.

#Between each charge how far did the vehicle travel on average?

At what speed? TM has said little about range other than EPA range, but much of it is speed dependent, just as it is with you current car.

#Was the vehicle driven accross the USA from East to West, and from West to East?

Now, that would have been big news indeed! Your can't prove a negative, but I'm going to say the absence of news indicates that this never happened.

Hi Ray. Unfortunately any sort of wind-driven generator works by taking a proportion of the kinetic energy out of the air. Behind the turning blades you must have a region of stiller (is that a word?) air.

Obviously the air can't be totally stationary otherwise no more air could flow through to turn the blades.

But this whole assembly of rotating blades plus the volume of slower moving air behind it does present a surprising amount of drag - even to air which doesn't quite manage to pass through the blades. You can sort of picture it as a 3D version of a bow-wave and wake created by the passage of a boat on a lake. Or a boat moored in a fast flowing river.

Consequently, the theoretical maximum energy which a wind turbine can extract from the wind blowing across it is just under 60%, known as the Betz limit. In practical cases, this figure is always lower due to mechanical losses in bearings and the like.

Sadly even this won't offset the energy needed to overcome the extra drag created by the wind turbine.

The following link doesn't discuss wind turbines, but looks at the work done in Truck aerodynamics research at the Ames Research Center. They hope to reduce truck drag coefficients by as much as 25 percent over the next 20 years. This is important work because although electric motors are quite capable of powering trucks and big-rigs, present-day electrical energy sources are not.

Any information on how the use of lights, heaters, airconditioning etc will impact teh 200 mile range estiomates? I live in Chicago and need the heaters about 5 months a year.

Mark Talaba

9:13am | Jul 27, 2007

Are you folks familiar with the new lithium iron phosphate battery being produced by Lithium Technology Corp.? LTC is based near Philadelphia. Very recently, they put their battery in a Prius, and got an electric-only 60 mile range, with a combined gas/electric 125mpg, and very good driving performance.

I know you have done amazing things with small battery arrays, but in the long haul (and especially for your 'production' models) this may be a much more practical solution.

Mark

CM

4:15pm | Jul 27, 2007

# Any information on how the use of lights, heaters, airconditioning etc will impact the
# 200 mile range estiomates? I live in Chicago and need the heaters about 5 months a year.

My rough calculations indicate that for every hour the 3Kw heater is on, range declines about 12.5 miles, but the heater isn't on constantly, it shuts off when the cabin gets warm enough. So, unless you're driving near the limit of the 200+ mile range, it isn't a concern. Another way to look at it is that if you did something silly like leave the top off and the heater running full blast, it would take 16 hours to run down the 50 Kwh battery pack! A/C and lights takes less power than the heater, and is less of a concern. Of course, if you want to save electricity, you can rely on the electrically heated seats that draw only 65 watts max.

# Are you folks familiar with the new lithium iron phosphate battery being produced
# by Lithium Technology Corp.?

Another one? Lets see, so far there is Valence, A123, Saft, and possibly others developing or manufacturing liIon batteries with iron phosphate electrodes. This type of LiIon avoids the thermal runaway and fire problems plaguing LiIon with Cobalt Oxide electrodes, though it does have slightly lower energy density. Power density is good, especially with the A123 cells. Be assured that Tesla Motors is aware of this type of battery (if not that particular company) and will consider using it in future models if it proves practical to do so.

Kingsley

8:01pm | Jul 29, 2007

Just curious...

If you want to be even more efficient, and if space allows, why not place in a "secondary" Lithium Ion Phosphate battery to be recharge while the car is in motion (forward or backwards)?

In otherwords, using the 4 wheels as generators to charge up the secondary battery. Then have an onboard computer to manage the use of the Primary and Secondary battery as if it is, from a Systems Administrator's point of view, Cluster.

If the electric car's battery and power system was based on the concept of Clustering: 2 front end servers (Car's Primary Battery) and 2 backend servers (Car's Secondary Battery) sharing the same storage unit (the electric car), you would have near 99.999% uptime of your server.

This way, you have self-contained or an enclosed system.

Just a thought if anyone thought about this?

PS: Instead of an electric roadster, an electric mini-van using the Cluster method would definitely be an attractive product to families across USA and Canada.

Ryan Lamansky / Kardax

9:35am | Jul 30, 2007

Kinglsey: You’re a victim of a common misconception. Alternators don’t “create” energy. They convert it.

Alternators function by converting negative torque into electricity… the more torque load, the more electricity you get. But negative torque slows the car down. If you wanted to capture enough energy to provide 100% of the motor’s needs, your negative torque would have to exactly match the positive torque of the motor, taking 100% of the forward motion, stopping the car dead in its tracks. It doesn’t work :)

And no, you can’t just take 50% and provide half its needs to give it double range. If you cause 50% negative torque, you take 50% of the car’s forward motion away, causing the motor to work twice as hard, giving the exact same range as you started with.

You could accurately say that our universe is designed to make unlimited sources of energy impossible :)

Mark Tomlinson

6:37pm | Jul 30, 2007

Ryan, right you are. Additionally, even with Tesla's super efficient motor/generator, you can't convert 100% of the electric energy into torque and you can't convert 100% of the torque into electricity. And you can't store 100% of the electricity you do generate. Hence, converting 50% of the torque to electricity and running that back to the motors results in significantly less than "the exact same range as you started with". An attempt to increase range simply decreases it.

Which brings us right back to where we started - regenerative braking. If we're going to grab any torque at all, it better be torque we were throwing away.

Janne Torvela

6:45pm | Jul 30, 2007

# Of course, if you want to save electricity, you can rely on the electrically heated seats that draw only 65 watts max.

Air-to-air heat pumps are all the rage these days. Why not modify the AC unit to be reversible. In typical mild conditions where the temperature doesn't drop too much below the freezing point, you get three to four times the amout of heat compared to the energy you put into running the pump. One part comes from the waste heat of the pump, and two parts come from chilling the air outside the car and dumping the heat into the cabin. You could even pull the heat out of the batteries' and motor's cooling loop.

So, 300 watts to run a compressor becomes 1 kW of warmth for the passengers. Easily enough to keep them comfortable.

Mark Tomlinson

6:58pm | Jul 30, 2007

Kingsley, an electric mini-van (presumably with a 200+ mile range) would indeed be attractive to families all across the US. The price tag wouldn't be, though. The Roadster's $98,000 price tag is driven by the technology and development costs - not the leather appointments. So Tesla is marketing to the exotic market (where $100,00 is considered reasonable) with the intention of appealing to wider audiences as the technology price comes down. Martin Eberhard frequently points out that flat screen tv's, VHS players, microwave ovens, refrigerators, electric lighting, indoor plumbing, and even the first automobiles were toys of the wealthy when they were first introduced.

Why not generate enough electricty while you drive to increase the miles before you recharge the battery's. Also have the car generate its own electricty to charge the battery's instead of plugging it in to the elect. grid Please hurry with the white star sedan so i can sell the accessory to provide self sustaining electical Bliss.

Andy

11:15am | Jul 31, 2007

I was wondering if you had any plans to build a truck version of your all electric vehicle? I own my own business here in Omaha, Nebraska and would love to own one of your vehicles only that I am a Decorative artist and have a need to carry a ladder and paints etc. A SUV version or truck version would be an ideal model for my business.
Please consider designing either an SUV or truck model.

Thanks and keep up the great work. Your roadster is absolutely stunning!!

TEG2

5:41pm | Jul 31, 2007

# Andy wrote on July 31st, 2007 at 12:15 pm
## I was wondering if you had any plans to build a truck version of your all electric vehicle?

That question has been asked a few times. Tesla has never mentioned plans for a truck, so you might want to investigate these:

It seems from other comments that people here want regenerative braking to be a separate function because they feel that they should be able to tell a sports car exactly what it is to do. This seems strange to me, as with a Corvette, there is no regenerative braking and no one wants the regenerative braking to be applied at some odd point in time because there is none. The Tesla Roadster should operate similarly to a Corvette, in which there is no concept of an extra regenerative braking mechanism. That is why the regenerative braking should be used to apply the frictional force that normal braking applies unless the brake pads would apply a greater force than the regenerative braking would otherwise apply, in which case the brake pads should be used to supplement the force of regenerative braking such that the car would brake exactly like it did not have regenerative braking.

In summary of what I said above, Corvettes do not have a separate regenerative braking system. Being a sports car like the Corvette, the Tesla Roadster should mimic how it brakes by using the force from regenerative braking only in place of all or part of the force (whichever is possible) from the brake pads.

By the way, if people really think that the regenerative braking and the regular brake pads should not both be controlled by the brake pedal, then they should understand how I feel about both the engine and the regenerative brake being controlled by the accelerator pedal. Someone said something about compromising. Well here is a compromise. Why not simply have 3 brake pedals in-place of the normal one. One will perform the logical function that I want and the other two will perform the illogical functions that some other people want. Another idea would simply to have some sort of software switch, to switch between the two according to people's personal preferences so that standard three pedal arrangement is preserved.

Lastly, if Tesla Motors wants to continue advertising their cars as being energy efficient, they should not ship a single vehicle that has the illogical feature of braking when the accelerator is at its zero position or any position in-between the one necessary to maintain a given velocity and the zero position. As an environmentalist and a science double major (and science double minor if mathematics and computer science count), I take offense to this idea. It is a blatant waste of resources and an illogical application of the physics that controls the vehicle's movement to the interface in which the vehicle's movement is controlled.

Richard

6:02am | Aug 2, 2007

In Martin Eberhard's and Marc Tarpenning's white paper, The 21st Century Electric Car, they imply that a well designed electric car should use regenerative braking in place of force from friction brakes by stating:

"Due to regenerative braking, even the friction brakes will encounter little wear. The only service that a well-designed electric car will need for the first 100,000 miles is tire service and inspection."

There is no possible way to require only tire service and inspection during the first 100,000 miles if regenerative braking is not used in place of force from the brake pads. This implies (by the laws of implication if I was to do a logical proof) that regenerative braking is to be used in place of the brakes in a well designed electric car. Therefore, according to Tesla Motor's own CEO, the Tesla Roadster will not be well designed if it ships with the illogical functionality of applying regenerative braking when the accelerator is not at an equilibrium position.

Does Tesla have a calualator somewhere, so I can see how much time it will take for a Tesla to pay for itself over say a $35,000 SUV that gets so many mpg. That would be really helpful. Thanks

Roy

6:20am | Aug 4, 2007

Matt: There is no point to such a calculator, $3/gal at 30mpg and $60000 price difference = 600,000 miles. You will never be able to justify the purchase of a Tesla Roadster on the basis of economy alone. That will come with future BlueStar.

Ronald Wose

8:59am | Aug 4, 2007

What is the total ampere hour usage rating of your existing battery pack, operating at street level at approx 55-65 MPH?

DDN

10:07pm | Aug 4, 2007

" Roy wrote on August 4th, 2007 at 7:20 am

Matt: There is no point to such a calculator, $3/gal at 30mpg and $60000 price difference = 600,000 miles. You will never be able to justify the purchase of a Tesla Roadster on the basis of economy alone."

A while back someone did a calculation like you are wondering about using each vehicle's maintenance schedule and came up ahead with the Tesla by about $4000 and this calculation included replacing the battery pack for around $20,000. Sorry I don't remember the blog entry where this was done.

David

TEG2

8:56pm | Aug 5, 2007

# Richard wrote on August 2nd, 2007 at 7:02 am
## the Tesla Roadster will not be well designed if it ships with the illogical functionality of applying regenerative braking when the accelerator is not at an equilibrium position.

RIchard,
Thanks for the blunt thoughts on the benefits of doing regen on the brake pedal instead of the "accelerator" pedal.
I agree (and have been saying repeatedly) that having the brake pedal be "friction brakes only" is a mistake.
Tesla undoubtedly had reasons for doing it the way they did in the roadster, and I suspect if they had been a bigger company with more time they might have better integrated with the brake system.

Now if the Tesla roadster had been coming out 10 years ago we wouldn't even be spending so much time debating the fine points of best regen implementation, but the fact is that regen is now more of a mainstream feature since hybrids have gained so much popularity in recent years. As had been pointed out, the hybrids from companies like Toyota do have regen come into play as part of the brake pedal action.

An ideal regen implementation (from an efficiency standpoint) would maximize the regen before having any friction braking action. Since the Tesla roadster is rear wheel drive / rear wheel regen only, they need a way to get some braking force started on the front wheels which is only possible with friction brakes now. Friction brakes are also a little hard to predict. Depending on rotor thickness, pad size, fluid pressure, and other factors, you may not know just how far the brake pedal has to be pressed before the friction brakes start to activate. Handling the transition from partial regen, then max regen, then regen + friction brakes can be tricky to do smoothly and safely.

A sophisticated system to activate regen based on brake pedal action, then slowly fade in the friction brakes just as regen gets to max seems like a laudable goal. But, I still think that regen ("negative torque") still has a place as part of the "accelerator"/"torque" pedal. My reasoning is this: you don't always want to have to switch your foot back and forth between the two pedals in situations where you are frequently slowing then accelerating. I give the following two examples of situations where it would be nice to be able to "modulate" your accel / deceleration using only one pedal:

#1: Driving on a twisty mountain road, or through rolling hills.
As you come out of a curve (or up a hill) you want more torque so you push harder on the "go pedal". As you approach the next curve (or start down the next hill) you want to slow down so simply easing off the pedal makes it less work than going back to the brake pedal. Dancing up and down on the one pedal to the beat of the curves or hills seems well suited to a sports car driving experience.

#2: Driving in heavy highway commute traffic where the flow keeps speeding up and slowing down. The concept of "stop and go traffic" is usually more "speed up and slow down traffic". If you can just modulate the "accelerator" / "torque" pedal to keep up with, and keep your distance from the rest of traffic it makes driving easier than having to bounce back on forth between the two pedals.

Both of these situations are ones where your speed needs to be somewhat sinusoidal. Various roads, and various traffic patterns lead to situations where you want to finesse your speed, and doing it with one pedal can be enjoyable and more relaxing.

On the other hand if you are driving through a residential neighborhood from stop to stop you are probably best using the brake pedal, and not having heavy automatic regen that drags you back down to 0mph in a big hurry. I still think "accelerator"/"torque" pedal regen (negative torque) is a good idea, but there should be some way to select from multiple profiles depending on the driving situation. Perhaps some selections ilke "city", "highway" and "hills" to pick from that adjusts the regen algorithm.

vfx

9:22am | Aug 7, 2007

Matt wrote :
"Does Tesla have a calualator somewhere, so I can see how much time it will take for a Tesla to pay for itself over say a $35,000 SUV that gets so many mpg."

Why would you compare a fast two seat sports car with almost no trunk to a large off road SUV? An Apple to Apple comparison would be a car with similar speeds and size.

How about a Ferrari or Lamborgini? These cars run $200 to $300K and the Tesla beats them from 0 to 60 MPH. My calculator says heck with their 8 to 10 MPG, I want to blow their doors off!

TEG2

10:49am | Aug 7, 2007

A bit more on regen...

Some people are used to large cars with automatic transmissions that like to "coast".
You let off on the accelerator pedal and the car just rolls along seeming never to want to slow down.
If you want to go faster you "blip" the accelerator pedal, then take your foot off again to coast.

As much as some people want Tesla vehicles to behave like that, I think it is a mistake.
Wind resistance hurts efficiency and a subtle (or not so subtle) hint to slow down will help your range and efficiency.
If you want to go fast then by all means use the go pedal with vigor, but when you relax your driving it is a good idea for the Roadster to slow itself down back to a more range efficient speed.

Tesla has said that the Roadster was more designed for driving dynamics and performance. The "pretty darn good" efficiency came for free with the technology they chose. Now that we are wishing that the range were even better we are rethinking what should be done from an efficiency standpoint rather than from a driving dynamics standpoint.

dean hewitt

10:56pm | Aug 7, 2007

Here is an interesting video on an electric airplane. They claim to have one of the most efficent electric motors in the world. How would this improve the range, etc of the roaster?

I have invented a system that will allow you to drive an electric vehicle for little or no cost, we are in the process of working with O.S.U. university in product developement. We are located in Tulsa OK, and plan to use a conversion system on todays automobiles so that we can increase the milege for fuel consumption. Our design can be used on all electric vehicles. Our web site is currently in construction and will have details of our product in the very near future..

HUEY

1:40pm | Aug 26, 2007

PERHAPSE ONE DAY WHEN ENOUGH OF THESE VEHICLES ARE ABUNDUNT ON THE HIGHWAY THE OVER VOLTAGE OF REGEN WHEN THE BATTERYS ARE FULL CAN BE WIRELESSLEY TRANSMITTED TO THE NEXT VEHICLE IN LINE AS TESLA WAS TRYING TO ACCOMPLISH.

Lance Humphries

7:26am | Aug 28, 2007

Have you ever considered making a vehicle as follows; motor 1 drives alternator, alternator goes to inverter, inverter drives electric engine(s). Motor 1 should be powered by compressed air, such as engineair.com.au. Adding an air tank to gas stations is realistic, in fact they may be able to convert a gas tank to an air tank.
I look forward to hearing from you.

SomeGuy

3:04pm | Sep 3, 2007

Put magnets on the wheels and generate the electricy to recharge batteries while wheels are spinning (during the ride).

John

5:19pm | Sep 3, 2007

The regenerative debate high lights for me an area of possible future improvement for the Tesla Roadster or its next generation offspring. All wheel drive. Not only would this allow more effective regen with a proper bake bias, but it would also improve the handling of the car and allow even quicker acceleration to be realised (granted with greater power required). This would certainly increase the sophistication, complexity, and hence cost of the car not to mention pushing the boundaries of the batteries power handling capabilities. 100% regenerative braking would probably stretch current technology beyond breaking point. At high speed such a system would need to be able to absorb enormous amounts of power and putting that into batteries as it is generated is probably not feasible. Ultra capacitors might fill that gap someday. Seamless integration of electric and hydraulic braking systems is the obvious challenge at this point. I would think ex ICE drivers would appreciate some regen on lift off of the throttle pedal. The free play at the beginning of brake pedal depression could be used to increase regen to maximum before the hydraulic brakes start working. A brake line pressure sensor could tell the system exactly when, in the brake pedal movement, that was up dating each time the brakes were used. Regen would then reduce as the brake line pressure increased to prevent it affecting brake bias at maximum braking effort. The hydraulic system under such a scheme would be unaffected if regen failed.

John

5:01pm | Sep 5, 2007

I would think that four independent motors each with their own inverter driving individual wheels would be the ultimate electric drive for a sports car. This would allow such interesting things to be done as electronically controlling the torque to each wheel to match the prevailing conditions each encountered. Back in the 80's car manufacturers played around with four wheel steering. For high speed changes of direction this had the effect of softening the yaw force demanded from the front tyres and hence reducing its destabilising effects. A yaw force could be developed with electronic drive by altering the torque balance between the wheels on the outside of the turn and those on the inside of the turn. In extreme cases the inside wheels could be put into regenerative mode to generate a negative torque.
With all wheel independent electric drive wheel torque could be altered to maintain maximum driving and regenerative effort even during large dynamic load shifts and on surfaces with variable grip and torque shifts could be computed to maintain balance and dynamic stability of the vehicle. We won’t know how fine handling a electric car can be until someone builds something like this. E4wd

Bryan Haaland

6:04pm | Sep 6, 2007

I have been toying around with the idea of a regen posibility based on the alternator of a standard vehicle or power generator. Is it possible to arrange a generator that will allow the car to recharge while moving? A high powered generator should be able to generate enough power to recharge on the move, thus allowing for a further distance before a full recharge of the batteries without creating to much friction on the axels causing reduced speed.

CM

7:14pm | Sep 12, 2007

That idea has been proposed and shot down many times, Bryan Haaland. Trying to drive around with the brakes on, or in this case, the regenerative brakes on, will have a bad effect on performance, and it will actually reduce the driving range! The extra electrical power needed by the motor to overcome that regenerative braking drag is greater than the electrical power produced by the regen generator.

The drag that slows down the car with regenerative braking comes not from friction, but from converting the forward momentum back into electrical power. The process is less than 100% efficient, so the energy regained by regenerative braking is less than the energy used to get up to speed. Still, regenerative braking is far better than old fashioned friction braking which is 0% efficient and doesn't regain any useful energy at all!

Adam R.

7:33pm | Sep 17, 2007

I drive a Prius, and I hate the ICE-imitating foot-off-the-pedal regen. Please make the Tesla's user selectable.

Dimitri Azulay

12:15pm | Sep 19, 2007

Have you considered the latest next-generation nanophosphate battery technology (originally developed at MIT) from A123 systems? This new battery technology puts the current Lithium Ion battery technology into the category of 'last generation' in terms of performance, longevity (and recharging times) and safety.http://www.a123systems.com/newsite/index.php#
Officially the fastest accelerating EV in existence runs on these batteries to achieve 0-60mph in 0.97 seconds (equivalent of 400bhp from its 175lbs battery pack)http://www.killacycle.com/

I wonder if you have considered installing a vertical axis motor beneath the hood of the Tesla.? Such a motor would require much less height per given diam' than a conventional turbine, and could run a 'genny' when slowing/braking, downhill running, side winds, and when stationary in wind. The motor I propose, has large blades which coarsen and 'feather' and provides in effect, a drive shaft with blades to one side only, with virtually nil resistance on the other.

I am retired, and seek no remuneration, but would just like to see this being used to good effect. See my Group!

John

7:33pm | Nov 15, 2007

You could take a Tesla roadster simplify the transmission to a single ratio and fit a second motor and transmission in the front driving the front wheels. For minimal weight gain and using components Tesla has already developed you could do an all wheel drive version. This would have better regen for improved range and quicker initial acceleration with improved handling under power.
Electric cars alter the packaging requirements for mechanical components i.e. no need for a drive shaft through the passenger compartment to do All Wheel Drive when wires will do. Electric cars are an exciting opportunity to think outside of the square. For instance with the ability to position all the heavy components low do you benefit from having four wheels over three. There could be aerodynamic and dynamic stability advantages to three wheels. The lack of conventional design of course would pose greater challenges gaining acceptance and people’s perceptions are more likely to be negative making the current vein the right one for now.

I was wondering how you deal with the torque being converted into the copper shaft mechanism. I have been told that it is impossible for the copper to sustain the abuse of slowing down a car. In other words, the copper would not be a usable alloy or metal composite to stop the car AT ANY SPEEDS. And how do you explain the very aspect of torque being generated from the removal of electrons from the copper?

does anyone know how to remove the energy from an electric generator without causing it to slow down?

Bill Howland

4:44am | Feb 27, 2008

Note to CM: Oh c'mon. A resistance bank with a fan? That would only be necessary if you drove tethered to an extension cord. By definition, the first time you apply the brakes, there HAS to have been considerable battery discharge. Since regenerative braking will only recover a fraction of what you initially put into it anyway, it follows that the battery can't be overcharged.

I know: How 'bout you're ontop of a tall hill and its 5 miles all the way down and you haven't even turned on the key yet. I guess for that ONE very RARE stop, the batteries will have to stop charging and the mechanical brakes will have to stop the car....

But seriously, for 99.9999999999% of the time, there will be CHARGING ROOM in the batteries.... This isn't obvious yet?

Re: the passenger heater. I'm satisfied with a resistance thing, if that's what it is. In my climate, its so cold outside that when I need a heater, the coefficient of performance drops to under 1 (so, there's no point, since the resistance heater would have a COP of 1).

Wind regeneration? C'mon. They already have a motor and a battery.... They dont want to put too much junk in the thing... A roadster has to be under 10,000 lbs.

- Bill.

Bill Howland

4:48am | Feb 27, 2008

Note to Roland Smith:

Yes, powerplants use synchronous machines... They spin at 1800 or 3600 rpm all the time, pretty much exactly. More load causes a slight rotational phase displacement, but the speed doesn't change.. The turbine powering it will use more steam with a larger load, obviously. but it does NOT slow down.

-bill.

John Gettings

1:40pm | Mar 16, 2008

Greg,

I see that others have written about this in the past. Has any thought been put into a "wind" generator mounted behind the grill of the car. My idea would be similar to a previous post, to have a "squirrel cage" style propeller, the width of the grill, that would spin a generator (or two) to produce additional electricity during driving, similar to regenerative braking but it would occur during acceleration, coasting and braking. The idea would be to extend the battery range by some amount and not to fully charge the batteries. If a flywheel is added to the propeller it would help spin the generator, once it was turning, to help reduce the "drag" effect. After the air passes through the propeller it could go on to cool controllers, batteries or occupants. I'm curious to find out what, if any, research has been done and what the outcome was.

- John

mohsin rasheed

10:45pm | Mar 23, 2008

Hello.
My name is mohsin and i m a student of Mechatronics Engineering. I m doing final year project on Regenerative Braking system. My whole system is driven by the motor which is powered by battery and during braking motor switches into generator which produces braking effect.
Your comments and informative suggestions will be appriciated and i m waiting for your anticipation.
Thank You

Brian Willoughby

4:15pm | Mar 31, 2008

This is an interesting topic, but I think some people misunderstand the nature of the differences between ICE and EV. Shifting to neutral in the CO mountains might improve fuel mileage, but staying in gear and using regen would improve mileage for the roadster. With gasoline ICE, the engine burns a certain amount of fuel at a given RPM no matter what amount of work is being done. Therefore, neutral is best downhill because the RPM is lower and less fuel is used. But you want to stay in gear and use regen in an EV, because you're actually creating "fuel" this way. Shifting to neutral downhill in the Tesla would be a waste, and your mileage would suffer.

My suggestion is to avoid complex regen controls for the Tesla roadster, and instead offer a neutral switch. Those who want to coast can put the transmission in neutral. We already have to do this with ICE. Engine-braking is always in effect for ICE unless you're in Neutral, whether Manual Transmission or Automatic Transmission. This solution still does not provide an answer for "how much" engine braking effect should occur when the Tesla is in regen mode, so that stiil needs to be dialed in for sports drivers versus grandma, but I think the question of coasting is easily solved.

iqrash javed

10:16am | Apr 12, 2008

my name is iqrash javed and i am a student of bachelors in mechatronics engineering in pakistan in the final year of my studies.i am doing the project with title" EXPERIMNTAL MODEL OF REGENERATIVE BRAKE SYSTEM " AS THIS IS NEW TECHNOLOGY I DONT KNOW THE SPECS OF MOTOR USED AND THE CONTROL CIRCIUTRY, OUR MODEL CONSISTS OF JUST TWO TYRES HANGED IN THE AIR ,I AM CONFUSED WHICH SPEED I SHOULD PROVIDE TO THE HANG TYRES TO HAVE EFFECTIVE REGEN RESPONSE WAITING FOR YOUR QUICK REPLY

mohammad

3:13am | Mar 24, 2009

it is really magic!!! but i wonder if it can control the rotation of a cylindrical shaft.. i am working on a project and it would be better for me if i could regenerate some energy from a shaft rotating initially at very high speeds and i want it to slow down gradually.. please inform me of any ways that i could use this technology

Rodrigo Céspedes

1:38pm | Sep 29, 2009

Hello, I wanted to ask, just out of curiosity, since you seem to me far the best mechanical engineers that there racing, whether as part of the mechanism for recharging the battery had thought of placing piezoelectric material in suspension so that energy back?. Perhaps be a good idea and I think they have not seen posed anywhere

Why not give drivers a knob on the dash they can twist to adjust the level of regen performed when you let off the accelerator?

To my way of thinking EV and hybrid makers are mentally "stuck" on using the traditional controls of ICE powered vehicles. Another example: Install a hand-brake like lever for regen, rather than associating regen with the brake pedal. Or for that matter a joystick.

So when you're coasting down a steep hill (like we do daily here in Colorado) you can simply stiffen up on the "handbrake" to achieve regen and control your speed down the hill. The next step from there is a downhill "cruise control" that limits your speed digitally to whatever you set.

Well what about drivers who don't want to fuss with a new and different control? FINE! A knob on the dash or the nav screen where they can adjust the amount of regen associated with the brake pedal.

These are exciting new cars! Give drivers the knobs and adjustments to customize and enjoy them to the max!